under pressure Materials Science, Univesity of Minnesota, Minneapolis, Minnesota 55455, USA NY , USA
|
|
- Charles Morrison
- 6 years ago
- Views:
Transcription
1 Spin transition in (Mg,Fe)SiO 3 perovskite under pressure Koichiro Umemoto a, Renata M. Wentzcovitch a Yonggang G. Yu a Ryan Requist b,1 a Minnesota Supercomputing Institute and Department of Chemical Engineering Materials Science, Univesity of Minnesota, Minneapolis, Minnesota 55455, USA b Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY , USA 1 2 Key words: spin transition, ferrous iron, atomic and magnetic configurations, perovskite, lower mantle, first principles Corresponding author, umemoto@cems.umn.edu, fax: addresses: umemoto@cems.umn.edu (Koichiro Umemoto), wentzcov@cems.umn.edu (Renata M. Wentzcovitch), yonggang@cems.umn.edu (Yonggang G. Yu), Ryan.Requist@physik.uni-erlangen.de (Ryan Requist). 1 Present address: Theoretische Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstrasse 7, Erlangen, Germany. Preprint submitted to Elsevier 29 September 2008
2 3 Abstract We present a density functional study of the pressure-induced spin transition in ferrous iron (Fe 2+ ) at the A site in MgSiO 3 perovskite. We address the influence of iron concentration and configuration (structural and magnetic), as well as technical issues such as the influence of the exchange correlation functional (LDA versus GGA) on the spin transition pressure. Supercells containing up to 160 atoms were adopted to tackle these issues. We show that there are preferred configurations for high-spin and low-spin iron and that the spin transition pressure depends strongly on iron concentration and all the issues above. Across the spin transition, irons move into the middle of distorted octahedra causing drastic changes in the d states configuration and a blueshift in the band gap. Such blueshift should decrease the contribution of ferrous iron to the electrical conductivity and increase its contribution to the radiative conductivity in the lower mantle. Both LDA and GGA results suggest that the spin transition can occur in the pressure range of the lower mantle and of previous experiments. The transition range can encompass the entire lower mantle passing through a mixed spin state caused by cation disorder and magnetic entropy. 2
3 21 1 Introduction The lower mantle of the Earth is believed to consist mainly of iron-bearing magnesium silicate perovskite, (Mg,Fe)SiO 3, with a little Al 2 O 3, and smaller amounts of (Mg,Fe)O and CaSiO 3. The presence of iron in perovskite affects several lower mantle properties: elastic and seismic properties (Kiefer et al., 2002; Li et al., 2005; Tsuchiya & Tsuchiya, 2006; Stackhouse et al., 2007), the post-perovskite transition pressure (Caracas & Cohen, 2005; Mao et al., 2005; Ono & Oganov, 2005; Stackhouse et al., 2006; Tateno et al., 2007) and electrical and thermal conductivities (Burns, 1993; Katsura et al., 1998; Xu et al., 1998; Badro et al., 2004), to mention a few. The spin state of iron in perovskite, which depends on its oxidation state, is a crucial factor in determining these properties. To date, there have been several studies to clarify what type of iron, ferrous (Fe 2+ ) and/or ferric (Fe 3+ ), and which site, A and/or the B, that are responsible for the spin transition at lower mantle pressures. However, there are some discrepancies between these studies An x-ray emission spectroscopy (XES) experiment by Badro et al. (2004) detected two distinct spin transitions, the first at about 70 GPa and the second at about 120 GPa. It was proposed that at 70 GPa the high-spin (HS) state transformed to a mixed-spin (MS) state and at 120 GPa all irons transformed to low-spin (LS). Infrared radiation was no longer absorbed after the transition to the LS state. Another XES experiment by Li et al. (2004) showed a gradual spin transition which was not completed at 100 GPa. It was suggested that in aluminum-free samples up to 100 GPa, all ferric irons acquired LS, while half of ferrous irons in the A site were in the intermediate-spin (IS) state. A gradual spin transition was also reported by a synchrotron Mössbauer spec- 3
4 46 47 troscopy experiment (Jackson et al., 2005) It was suggested that ferric iron was responsible for the spin transition which ended around 70 GPa The spin transitions in ferrous and ferric iron have been intensively investigated also theoretically (Cohen et al., 1997; Li et al., 2005; Hofmeister, 2006; Zhang & Oganov, 2006; Stackhouse et al., 2007; Bengtson et al., 2008). Calculations so far showed that ferric iron undergoes a spin transition at lower mantle pressures. The transition pressure was found to depend strongly on how ferric iron replaces Mg and Si, with two ferric irons or one ferric iron and one aluminum (Li et al., 2005; Zhang & Oganov, 2006; Stackhouse et al., 2007). This may be related to the observed gradual spin transition in ferric iron. The choice of the exchange-correlation functional used in these calculations, the local-density approximation (LDA) or the generalized-gradient approximation (GGA), affects strongly the transition pressure as well (Stackhouse et al., 2007; Bengtson et al., 2008). GGA studies in ferrous iron have insisted that the spin transition should not take place at lower mantle conditions while LDA studies show that the transition could take place within lower mantle pressures but at still rather high values (Hofmeister, 2006; Zhang & Oganov, 2006; Stackhouse et al., 2007; Bengtson et al., 2008). It is still hard to say that all of the properties of the spin transition in ferrous iron whether the transition is sharp or gradual, whether or not the transition occurs in the lower mantle, and what are the corresponding changes in the infrared absorption spectrum have been accounted for In the present first-principles study, we investigate further the spin states (HS, LS, and IS states) in ferrous iron in Mg 1 x Fe x SiO 3 perovskite. For ferrous iron, HS, LS, and IS states have magnetic moments per iron of 4µ B (5 majorityspin and 1 minority-spin electrons, S = 2), 0µ B (3 and 3, S = 0), and 2µ B (4 4
5 and 2, S = 1), respectively. The dependence of the spin transition pressure on iron concentration x, atomic configurations, and magnetic ordering is clarified. Both LDA and GGA results suggest that the spin transition through a MS state occurs within the pressure range of experiments and of the lower mantle. We also address the change of atomic and electronic structures across the spin transition, which should greatly affect thermal and electrical conductivities Computational method Calculations were performed using LDA and GGA (Perdew & Zunger, 1981; Perdew et al., 1996). The pseudopotentials for Fe, Si, and O were generated by Vanderbilt s method (Vanderbilt, 1990). The valence electronic configurations used are 3s 2 3p 6 3d 6.5 4s 1 4p 0, 3s 2 3p 1, and 2s 2 2p 4 for Fe, Si, and O. Core radii for all quantum numbers l are 1.8, 1.6, and 1.4 a.u. for Fe, Si and O. The pseudopotential for Mg was generated by von Barth-Car s method. Five configurations, 3s 2 3p 0, 3s 1 3p 1, 3s 1 3p 0.5 3d 0.5, 3s 1 3p 0.5, and 3s 1 3d 1 with decreasing weights 1.5, 0.6, 0.3, 0.3, and 0.2, respectively, were used. Core radii for all quantum numbers l are 2.5 a.u.. The plane-wave cutoff energy is 40 Ry. As described later, we used several atomic configurations with various supercell sizes and shapes. The k-point meshes used for the Brillouin zone sampling in each cell are fine enough to achieve convergence within 1mRy/iron in the total energy. They are described in the captions of figures showing atomic configurations. We used variable-cell-shape molecular dynamics (Wentzcovitch, 1991; Wentzcovitch et al., 1993) for structural optimization under arbitrary pressures. 5
6 95 3 Results and Discussion Effect of iron concentration First we investigate the effect of iron concentration on the spin transition. For each iron concentration from 6.25% (x = ) to 100% (x = 1), the smallest unit cell is taken (Fig. 1). Hereafter we refer to them as configuration 0 in order to distinguish them from other configurations which will be generated later. Only the FM state is considered for the HS state in configuration 0. Calculated HS-LS transition pressures are shown by blue points in Fig. 2. GGA gives higher transition pressures, by 50 GPa, than LDA for all iron concentrations. The transition pressure decreases with increasing iron concentration, being 13 GPa (62 GPa) by LDA (GGA) at x = 1. Below x = 0.25 the transition pressure is approximately constant. This trend agrees with Bengtson et al. (2008) but disagrees with Stackhouse et al. (2007), where the transition pressure in FeSiO 3 (calculated to be 284 GPa) was higher than in Mg Fe SiO 3. We have not found a spin transition to the IS state; the IS state always has higher enthalpy than the LS state in our calculations The HS-LS spin transition is accompanied by significant change in the atomic structure (Fig. 3). The size of ferrous iron decreases through the transition. This decrease destablizes iron in the high symmetry site (with z Fe = ±0.25) where iron sits in the HS state. Optimization from an initial geometry for the HS iron atom displaced brings it back to the symmetric position. In the HS state, irons are 8-fold coordinated in a bicapped trigonal prism. Across the spin transition, five bonds among eight shorten and the other three lengthen. In particular, one of the two longest Fe-O bonds in the HS state shortens from 6
7 Å to 1.830Å at 120 GPa and x = (LDA). This 16% decrease of the Fe-O bond is much larger than that expected from the volume reduction of just 0.4%. As a result, in the LS state, irons end up being 6-fold coordinated and in strongly distorted octahedra. The displacement of irons is crucial for the spin transition. Without the displacement, the spin transition does not occur at least up to 180 GPa for all iron concentrations. The displacement plays an important role in the electronic structure as discussed later in section Effect of atomic and magnetic ordering Next we study the effects of atomic and magnetic ordering on the spin transition. For x = 0.5, we prepare five atomic configurations (Fig. 4). The first three configurations have unit cells of 20 atoms, while configurations 4 and 5 are generated in the supercell. This is done to take into account special distributions of irons along the (110) plane of the perovskite structure, whose importance will be clarified later. FM configuration 1 is the same as HS configuration 0. The AFM states have an additional degree of freedom, the spin of iron, leading to two or three spin configurations for each atomic configuration. AFM 1 is stable in the atomic configurations 1, 2, and 5, while AFM 2 is stable in the atomic configurations 3 and 4. Enthalpies depend on atomic configurations and spin state and the dependence becomes stronger as pressure increases and iron-iron distances decrease (Fig. 5 (a) and (b)). At higher pressure the AFM states have lower enthalpies than the FM states, while at lower pressures the enthalpy difference between the FM and AFM states is very small. The spin transition pressure depends on the atomic configuration as shown in Fig. 5 (c). Within this set of configurations it varies by 7
8 GPa. Configurations 4 and 5 have the lowest transition pressures, 49 and 52 GPa. Because of its low enthalpy and transition pressure, configuration 4, with irons preferentially on the (110) plane, is important. From this we infer that similar cations prefer to exist in the same column For x = 0.125, which is close to the expected concentration in the lower mantle and those investigated experimentally, we consider fourteen atomic configurations shown in Fig. 6. For configurations 1 to 9, we use supercells with 80 atoms. Configurations 3, 4, 7, 8, and 9 correspond respectively to configurations referred to as SSM2, 3, 4, 1, and 5 in Stackhouse et al. (2007). Configurations 10, 11, and 12 are extensions of configurations 3, 4, and 5 for x = 0.5. In configurations 10 (1 1 4 supercell with 80 atoms) and 11 ( supercell with 160 atoms), irons are placed on (001) and (110) planes, respectively. In addition, we prepared configurations 13 (4 1 1 supercell with 80 atoms) and 14 (1 4 1 supercell with 80 atoms) in which irons are placed on (010) and (100) planes. Again, we can see the enthalpy dependence on atomic configurations for each spin state, the dependence becoming more accentuated with increasing pressure (Fig. 7 (a) and (b)). Configuration 11 has the lowest enthalpy for AFM-HS and LS states, whereas configuration 10 has the lowest for FM-HS at high pressure, but, its enthalpy is very close to that of configuration 11 FM. Hence, irons tend to order in the (110) plane like the case of x = 0.5. These results together indicate that the HS-LS transition pressure depends simultaneously on the cation and magnetic ordering (Fig. 7 (c)). Its dependence on the magnetic ordering is not so large though. For most atomic configurations, transition pressures from or to FM and AFM states differ by 5 GPa. For configurations 2, 7, and 12, the differences are larger but still GPa at most. Variation in the tranition pressures for 8
9 atomic configurations 1 9 is not so large either, 15 GPa, being consistent with the previous calculation on SSM1 5 configurations (Stackhouse et al., 2007). In contrast, configuration 11 AFM, in which irons are placed on the (110) plane as in configuration 4 of x = 0.5, has a LDA transition pressure as low as 56 GPa which is significantly smaller than those of other configurations. Therefore, for the HS-LS transition, the effect of cation ordering, i.e., elastic and chemical interactions, is much stronger than that of the magnetic ordering, i.e., the exchange interaction. We then generated equivalent AFM configurations containing irons in the (110) plane for other iron concentrations as well and calculated the spin transition pressures (red points in Fig. 2). It is clear that ordering of irons in the (110) plane greatly reduces the transition pressure at low iron concentration Electronic structure The electronic structure changes with the spin transition as shown in Fig. 8. Although LDA is known to underestimate the band gap by as much as 50%, it offers trends that are in good agreement with experiments. For configuration 0 in the HS state at x = and 120 GPa, there is a small band gap between the first and second peaks of the minority-spin d states of iron. At 0 GPa, this band gap vanishes and the band structure is metallic. On the other hand, as pressure increases, the band structure becomes nonmetallic and the band gap increases, since Fe-O bondlengths decrease and the crystal field splitting increases. From the spatial distributions of wave functions shown in Fig. 8, we see that iron d states do not simply split into lower e g and higher t 2g states as usually assumed (Li et al., 2004; Hofmeister, 2006). This is because the A site 9
10 does not have cubic symmetry. It is surrounded by eight oxygens in a bicapped trigonal prism configuration. In the LS state, as a result of the displacement of iron to the middle of distorted octahedra, the d states split into the lower occupied t 2g -derived and the higher empty e g -derived states. Then the band gap greatly increases, indicating a blueshift across the spin transition (Badro et al., 2004, 2005). This is opposite to the case of magnesiowüstite in which a redshift was reported (Tsuchiya et al., 2006; Goncharov et al., 2006; Keppler et al., 2007). The LDA band gaps for the HS and the LS states at 120 GPa are 0.3 ev and 1.75 ev, respectively In all other configurations, we observed iron displacement and blueshift in the band gap across the spin transition. Since in configuration 11 the distance between irons are smaller than in configuration 0, the electronic bands originated from iron d states are more dispersive. The band gaps (0.2 ev for the AFM state and 1.45 ev for the LS state) are slightly smaller than those of configuration 0. These values are lower bounds, because the LDA tends to underestimate the band gap. Therefore, in the absence of shallow or deep defect levels in the gap, iron-bearing perovskite in the LS state should not absorb near-infrared radiation and should be transparent to most of the blackbody radiation from the core at 2,500 K whose peak appears at 1.07 ev (1159 nm). It is consistent with the experimental observation that the radiation of the Nd:YAG laser with the wave length of 1064 nm could not heat (Mg 0.9,Fe 0.1 )SiO 3 in the LS state at 120 GPa (Badro et al., 2004). The blueshift across the spin transition should reduce the electrical conductivity due to thermally excited electrons and increase the radiative conductivity in the lower mantle. 10
11 Structural disorder and configurational entropic stabilization We have seen that configurations with irons close to each other in the (110) plane (configuration 4 with x = 0.5 and configuration 11 with x = 0.125) have low enthalpies and spin transition pressures. Irons prefer to order especially at high pressure and in the LS state. The extreme limit is the decomposition into pure phase: MgSiO 3 and FeSiO 3. In fact, static enthalpy calculation for x = indicates that the dissociated phases have lower enthalpy than any configuration generated so far (Fig. 9). But at high temperature the configurational entropy stabilizes Mg Fe SiO 3 against the dissociation products. For reference we may assume Mg Fe SiO 3 is an ideal solid solution of MgSiO 3 and FeSiO 3, the configurational entropy S conf per Mg Fe SiO 3 is given by S conf = k B (x log x+(1 x) log(1 x)) where k B is Boltzmann constant and x = The configurational entropy of the dissociated products is 0 (x = 0 and 1). The difference in Gibbs free energy between Mg Fe SiO 3 in configuration 0 and the dissociated products, G, G = H T S conf = H Mg0.875 Fe SiO 3 (0.875H MgSiO H FeSiO3 ) T S conf. (1) When G < 0, Mg Fe SiO 3 is energetically stable with respect to the dissociation. Fig. 9 shows that G is negative at low pressure and high temperature; at 26 GPa, configuration 0 should be stable with respect to the dissociation over 1,300 K by LDA ( 600 K by GGA). This is consistent with the synthesis of (Mg,Fe)SiO 3 perovskite with 10% iron concentration at 26 GPa and 2,000 K (e.g., Kudoh et al. (1990); Parise et al. (1990); Fei et al. (1994); Jackson et al. (2005)). Although at 300 K the dissociation products are energetically stable with respect to Mg Fe SiO 3 ( G > 0), 11
12 there has not been any experimental report of the dissociation, as far as we know. This could indicate that cation diffusion among the A sites in quenched samples is suppressed or not fast enough to induce the dissociation in experimental time scales at room temperature. Then, it may be assumed that in Mg Fe SiO 3 all atomic configurations appear at least locally at room temperature. According to this assumption, the spin transition should occur in each configuration with different transition pressures, giving rise to a MS state even at 0 K. It should be noted that this MS state is fundamentally different from the IS state; in the MS state, a fraction of the HS irons transforms to the LS state and both states exist simultaneously. Our calculations have not stabilized irons in the IS state. The transition pressure should be continuous between lower and higher bounds. The higher bound of the transition pressure is given by that of configuration 0, i.e., 98 (158) GPa by LDA (GGA). The lower bound should be that of configuration 11 or of FeSiO 3 : 56 or 16 GPa (116 or 76 GPa) by LDA (GGA), respectively. However, these configurations assume (110) plane segments and FeSiO 3 islands of infinite lengths. The transition pressures we calculated correspond to these limit lengths. These lengths are unlikely to occur in practice. Instead, it is appropriate to suppose that there are (110) iron plane segments and 3D FeSiO 3 islands of various lengths. Larger planes and islands should have lower transition pressures. Configuration 0 corresponds to the lower limits for the (110) plane segment and FeSiO 3 island lengths. Variation in plane segment and island sizes should also lead to variation in spin transition pressure. This argument suggests a gradual spin transition in ferrous iron in the A sites between 16 and 98 GPa (76 and 158 GPa) by LDA (GGA) if cation diffusion is not significant. Therefore, both LDA and GGA results indicate that the gradual spin transition in ferrous iron in the A site can occur in the pressure range of previous experiments and relevant 12
13 to the lower mantle. The gradual spin transition observed by Li et al. (2004) may be due to a transition between a MS state, due to random configurations, to the LS state, as opposed to a transition from the IS state, which has higher enthalpy than other states, to the LS state Fig. 9 indicates that G by LDA becomes positive beyond 40 GPa in the lower mantle, i.e., that Mg Fe SiO 3 with completely random iron distribution is no longer stable beyond 40 GPa. On the other hand, GGA indicates that Mg Fe SiO 3 with random cation distribution should be stable up to 120 GPa, i.e., almost in the entire lower mantle, except in the D layer. Reality may exist somewhere between LDA and GGA results. Beyond the dissociation pressure, diffusion could start at the high temperatures of the lower mantle. Although we do not know how fast diffusion occurs, it should not be fast enough to induce the complete dissociation since (Mg,Fe)SiO 3 is experimentally reported to be stable at lower mantle conditions (Serghiou et al., 1998). Cation diffusion should facilitate clustering of irons and increase the number of iron-(110) plane segments and FeSiO 3 islands. Sample annealing may enhance cation diffusion and clustering of irons at high pressure and, consequently, facilitate the spin transition. This could be related to the complete spin transition up to 120 GPa in the experiment with sample annealing by Badro et al. (2004). In the lower mantle, cation diffusion and iron clustering might be further faciliated at high temperature in geological time scale. Hence the spin transition pressure could be lower in the lower mantle than in laboratories, inferring a possible relationship between the spin transition with the blueshift in the band gap and magnetic satellite observations that the electric conductivity ceases to increase in the mantle at depths greater than 900 km ( 35 GPa) (Constable & Constable, 2004; Kuvshinov & Olsen, 13
14 ). Clustering of irons implies separation of (Mg,Fe)SiO 3 into Fe-rich and Fe-poor segments with lower spin transition pressures. Iron-rich segments can exist under pressure because the maximum solubility of FeSiO 3 into MgSiO 3 increases with increasing pressure (Mao et al., 1997; Tateno et al., 2007) while it is up to 12% only at low pressure, i.e., 26 GPa as measured by Fei et al. (1996) Effect of magnetic entropy In addition to configurational entropy, magnetic entropy is another important factor at high temperatures. It is known that in magnesiowüstite magnetic entropy leads to a gradual spin transition through a MS state (Sturhahn et al., 2005; Tsuchiya et al., 2006; Lin et al., 2007) The LS iron fraction, n, in paramagnetic MS state above the Curie or Néel temperatures is estimated by 305 n(p, T ) = 1 + m(2s + 1) exp ( H LS HS (P ) k B xt 1 ), (2) where k B is the Boltzmann constant, x is the iron concentration (x = 0.125), H LS HS (P ) is the relative enthalpy of the LS state per Mg 1 x Fe x SiO 3 with respect to the HS state, S is the iron spin quantum number (S = 2 for HS and S = 0 for LS), and m is the electronic configuration degeneracy (Tsuchiya et al., 2006). In the present case, m = 1 for both HS and LS states, since the degeneracy is lifted even in the HS state due to the low symmetry of the iron site (see Fig. 8 for x = 0.125) We do not know the Curie or Néel temperatures of this system, but we can discuss the validity of eq. 2 in the lower mantle. The enthalpy difference be- 315 tween the FM and the AFM states ( H AFM FM = H AFM H FM ) in each 14
15 configuration increases with increasing pressure (Fig. 7). In configuration 11, whose H AFM FM is largest among the 14 configurations, the LDA values of H AFM FM at 26 and 125 GPa are 0.27 and 8.9 mry per iron. These values correspond to 45 K and 1350 K, respectively. Since these values are smaller than lower mantle temperatures at these pressures, it is reasonable to assume that (Mg,Fe)SiO 3 exists in a paramagnetic state in the lower mantle, i.e., above 2,000 K, even when the irons are close to each other. Therefore we can estimate the LS iron fraction n in the mantle using eq. 2. Figure 10 shows n(p, T ) for x = 0.125, where H LS HS is H LS H FM for configuration 0 and H LS (H AFM + H FM )/2 for configuration 11. Like in magnesiowüstite, the MS state region between HS and LS states is found to be wider at higher temperatures. In the lower mantle, even in iron-ordered configurations, the spin transition should not be complete at the CMB for x = At room temperature, the pressure range of the MS state estimated by eq. 2 is less than 10 GPa. If eq. 2 is not adequate at room temperature and high pressure (in fact H AFM FM in configuration 11 at the static transition pressure is over 300 K), this pressure range should be narrower. Therefore, at room temperature the occurrence of the MS state should be mainly due to atomic disorder, not due to the magnetic entropy effects Conclusions The spin transition from the HS to the LS state in ferrous irons at the A site in (Mg,Fe)SiO 3 perovskite has been investigated by first principles. We found that a displacement of irons from the preferred magnesium site leading to a change in iron coordination number is vital for the occurrence of the spin 15
16 transition. We also found a strong dependence of the transition pressure on types of exchange-correlation functionals, iron concentration, and atomic and magnetic orderings. Our calculations suggest a gradual spin transition with MS state between the HS and the LS state in the pressure range of the lower mantle of the Earth as observed in previous experiments. We also showed there is a significant blueshift in the electronic gap across the spin transition. This property is crucial for understanding electrical and radiative conductivities There are several important factors we have not considered in the present study: vibrational entropies, the effect of ferric iron, impurities and defects, such as aluminum and oxygen vacancy, the strongly correlated nature of irons (the Hubbard U), and the post-perovskite transition. The vibrational entropy is necessary for calculating phase boundaries at finite temperatures. Phonon frequencies involving iron displacements should change significantly across the HS-LS transition, because the atomic environment around iron changes drastically. Inclusion of the Hubbard U should be important. In the case of magnesiowüstite, the Hubbard U is essential to predict its electronic properties; without U, the HS state was calculated to be metallic (Tsuchiya et al., 2006). In the present case, however, our calculations without the Hubbard U already showed both HS and LS states have nonmetallic band structure at lower mantle pressure and hence the charge density calculated from the fully occupied states should be reliable. Still the Hubbard U might change our results. The smaller band gap of the HS state than the LS state is expected to give a higher U value. Then, the inclusion of the Hubband U could lower the transition pressure further. The band gap of the HS state might be increased with the Hubbard U. These important factors still remain to be investigated. Nevertheless, the effects uncovered here should still be important in all future 16
17 366 calculations. 367 Acknowledgments We would like to thank Professor D. Yuen for helpful comments. Calculations in this work were performed using the Quantum-ESPRESSO package (Baroni et al.) at the Minnesota Supercomputing Institute and at Indiana University s BigRed system. The spatial distribution of wave functions in Fig. 8 was visualized by XCrySDen (Kokalj, 2003). This research was supported by NSF/EAR , ITR (VLab), NSF/DMR (ITAMIT), and the Minnesota Supercomputing Institute. 375 References Badro, J., J. P. Rueff, G. Vanko, G. Monaco, G. Fiquet, and F. Guyot (2004), Electronic Transitions in Perovskite: Possible Nonconvecting Layers in the Lower Mantle, Science 305, Badro, J., G. Fiquet, and F. Guyot (2005), Thermochemical State of the Lower Mantle: New Insights From Mineral Physics, Geophysical Monograph 106, Baroni S., A. Dal Corso, S. de Gironcoli, P. Giannozzi, C. Cavazzoni, G. Ballabio, S. Scandolo, G. Chiarotti, P. Focher, A. Pasquarello, K. Laasonen, A. Trave, R. Car, N. Marzari, and A. Kokalj, Bengtson, A., K. Persson, and D. Morgan (2008), Ab initio Study of the composition dependence of the pressure-induced spin crossover in perovskite (Mg 1 x,fe x )SiO 3, Earth Planet. Sci. Lett., 265, Brown, J. M. and T. J. Shankland (1981), Thermodynamic parameters in the 17
18 Earth as determined from seismic profiles, Geophys. J. R. Astr. Soc. 66, Burns, R. G. (1993), Mineralogical Applications of Crystal Field Theory, Cambrudge University Press. Caracas, R. and R. E. Cohen (2005), Effect of chemistry on the stability and elasticity of the perovskite and post-perovskite phases in the MgSiO 3 - FeSiO 3 -Al 2 O 3 system and implications for the lowermost mantle, Geophys. Res. Lett. 32, L Cohen, R. E., I. I. Mazin, and D. G. Isaak (1997), Magnetic Collapse in Transition Metal Oxides at High Pressure: Implications for the Earth, Science 275, Constable, S. & C. Constable (2004), Observing geomagnetic induction in magnetic satellite measurements and associated implications for mantle conductivity, Geochem. Geophys. Geosyst. 5, Q01006, doi: /2003gc Fei, Y., D. Virgo, B. O. Mysen, Y. Wang, and H. K. Mao (1994), Temperaturedependent electron delocalization in (Mg,Fe)SiO 3 perovskite, Am. Mineral. 79, Fei, Y., Y. Wang, and L. W. Finger (1996), Maximum solibility of FeO in (Mg,Fe)SiO 3 -perovskite as a function of temperature at 26 GPa: Implication for FeO content in the lower mantle, J. Geophys. Res. 101, Goncharov, A. F., V. V. Struzhkin, and S. D. Jacobsen (2006), Reduced Radiative Conductivity of Low-Spin (Mg,Fe)O in the Lower Mantle, Science 312, Hofmeister, A. M. (2006), Is low-spin Fe 2+ present in Earth s mantle?, Earth Planet. Sci. Lett. 243, Jackson, J. M., W. Sturhahn, G. Shen, J. Zhao, M. Y. Hu, D. Errandonea, J. 18
19 D. Bass, and Y. Fei (2005), A synchrotron Mössbauer spectroscopy study of (Mg,Fe)SiO 3 perovskite up to 120 GPa, Am. Mineral. 90, Katsura, T., K. Sato, and E. Ito (1998), Electrical conductivity of silicate perovskite at lower-mantle conditions, Nature 395, Keppler, H., I. Kantor, and L. S. Dubrovinsky (2007), Optical absorption spectra of ferropericlase to 84 GPa, Am. Mineral. 92, Kiefer, B., L. Stixrude, and R. M. Wentzcovitch (2002), Elasticity of (Mg,Fe)SiO 3 -Perovskite at high pressures, Geophys. Res. Lett. 29, L Kuvshinov, A. & Olsen, N., 2006, A global model of mantle conductivity derived from 5 years CHAMP, Orsted, and SAC-C magnetic data, Geophys. Res. Lett. 33, L Kokalj, A. (2003), Computer graphics and graphical user interfaces as tools in simulations of matter at the atomic scale, Comp. Mater. Sci. 28, Kudoh, Y., C. T. Prewitt, L. W. Finger, A. Darovskikh, and E. Ito (1990), EFFECT OF IRON ON THE CRYSTAL STRUCTURE OF (Mg,Fe)SiO 3 PEROVSKITE, Geophys. Res. Lett. 17, Li, J., V. V. Struzhkin, H.-k Mao, J. Shu, R. J. Hemley, Y. Fei, B. Mysen, P. Dera, V. Prakapenka, and G. Shen (2004), Electronic spin state of iron in lower mantle perovskite, Proc. Nat. Acad. Sci. 101, Li, L., J. P. Brodholt, S. Stackhouse, D. J. Weidner, M. Alfredsson, and G. D. Price (2005), Electronic spin state of ferric iron in Al-bearing perovskite in the lower mantle, Geophys. Res. Lett. 32, L Lin, J. F., G. Vankó, S. D. Jacobsen, V. Iota, V. V. Struzhkin, V. B. Prakapenka, A. Kuznetsov, and C. S. Yoo (2007), Spin Transition Zone in Earth s Lower Mantle, Science 317, Mao, H. K., G. Shen, R. J. Hemley (1997), Multivariable Dependence of Fe-Mg 19
20 Partitioning in the Lower Mantle, Science 278, Mao, W. L., Y. Meng, G. Shen. V. B. Prakapenka,. A. J. Campbell, D. L. Heinz, J. Shu, R. Caracas, R. E. Cohen, Y. Fei, R. J. Hemley, and H. K. Mao (2005), Iron-rich silicates in the Earth s D layer, Proc. Nat. Aca. Sci. 102, Parise, J. B., Y. Wang, A. Yeganeh-Haeri, D. E. Cox, and Y. Fei (1990), CRYS- TAL STRUCTURE AND THERMAL EXPANSION OF (Mg,Fe)SiO 3 PER- OVSKITE, Geophys. Res. Lett. 17, Perdew J. P. and A. Zunder (1981), Self-interaction correction to densityfunctional approximations for many-electron systems, Phys. Rev. B 23, Perdew J. P., K. Burke, M. Ernzerhof (1996), Generalized Gradient Approximation Made Simple, Phys. Rev. Lett. 77, Ono, S. and A. R. Oganov (2005), In situ observations of phase transition between perovskite and CaIrO 3 -type phase in MgSiO 3 and pyrolitic mantle composition, Earth Planet. Sci. Lett. 236, Serghiou, G., A. Zerr, and R. Boehler (1998), (Mg,Fe)SiO 3 -Perovskite Stability Under Lower Mantle Conditions, Science 280, Stackhouse, S., J. P. Brodholt, D. P. Dobson, and G. D. Price (2006), Electronic spin transitions and the seismic properties of ferrous iron-bearing MgSiO 3 post-perovskite, Geophys. Res. Lett. 33, L12S03. Stackhouse, S., J. P. Brodholt, and G. D. Price (2007), Electronic spin transitions in iron-bearing MgSiO 3 perovskite, Earth Planet. Sci. Lett. 253, Sturhahn, W., J. M. Jackson, & J. F. Lin (2005), The spin state of iron in minerals of Earth s lower mantle, Geophys. Res. Lett. 32, L Tateno, S., K. Hirose, N. Sata, and Y. Ohishi (2007), Solubility of FeO in 20
21 469 (Mg,Fe)SiO 3 perovskite and the post-perovskite phase transition, Phys Earth Planet. Inter. 160, Tsuchiya, T., R. M. Wentzcovitch, C. R. S. da Silva, and S. de Gironcoli (2006), Spin Transition in Magnesiowüstite in Earth s Lower Mantle, Phys. Rev. Lett. 96, Tsuchiya, T. and J. Tsuchiya (2006), Effect of impurity on the elasticity of perovskite and postperovskite: Velocity contrast across the postperovskite transition in (Mg,Fe,Al)(Si,Al)O 3, Geophys. Res. Lett. 33, L12S04. Vanderbilt D. (1990), Soft self-consistent pseudopotentials in a generalized eigenvalue formalism, Phys. Rev. B 41, R7892. Wentzcovitch R. M. (1991), Invariant molecular-dynamics approach to structural phase transitions, Phys. Rev. B 44, Wentzcovitch R. M., J. L. Martins, and G. D. Price (1993), Ab Initio Molecular Dynamics with Variable Cell Shape: Application to MgSiO 3, Phys. Rev. Lett. 70, Xu Y., C. McCammon, and B. T. Poe (1998), The Effect of Alumina on the Electrical Conductivity of Silicate Perovskite, Science 282, Zhang, F., and A. R. Oganov (2006), Valence state and spin transitions of iron in Earth s mantle silicates, Earth Planet Sci. Lett. 249,
22 Fig. 1. Atomic arrangements of irons and magnesiums in configuration 0 for various iron concentrations x. Red and green spheres denote iron and magnesium. Blue polyhedra represent SiO 6 octahedra. The unit cells denoted by black lines contain 80 atoms (2 2 1 supercell) for x = , 40 atoms ( supercell) for x = and 20 atoms for other x. The k point grids used for these supercells are for x = and x = and for others. 22
23 Fig. 2. Calculated spin transition pressures. Blue and red points denote calculated values with configuration 0 and the iron-(110) plane configuration. Dashed lines and color bands are guides to the eye. 23
24 Fig. 3. Local atomic structure around iron in configuration 0 at 120 GPa optimized by LDA. Numbers denote Fe-O bond lengths in Å. 24
25 Fig. 4. Five atomic configurations of iron and magneiums for x = 0.5. Red and green spheres denote iron and magnesium respectively. For the AFM state, red and white spheres denote irons with up and down spins. The smaller and larger black rectangles represent the unit cell with 20 atoms and with 40 atoms ( supercell), respectively. The k point grids used for these supercells are for the 20-atoms unit cells and for the 40-atoms unit cells. 25
26 Fig. 5. Calculated (a) enthalpies at 0 GPa and (b) at 150 GPa and (c) spin transition pressures for each atomic configuration with x =
27 Fig. 6. Fourteen atomic configurations with x = Red and green spheres denote iron and magnesium. The unit cells denoted by the black lines contain 80 atoms in all configurations except for configuration 11, which contains 160 atoms. The k point grids used for these supercells are for configurations 1 through 10, for configuration 10, for configurations 11 and 12, for configuration 13, and for configuration
28 Fig. 7. Calculated (a) enthalpies at GPa and (b) 150 GPa and (c) spin transition pressures for each atomic configuration with x =
29 Fig. 8. Electronic density of states (DOS) and probability densities corresponding to groups of wave-functions at each peak of the DOS at 120 GPa for x = States filled with electrons are hatched. Energy is measured from the top of the MgSiO 3 valence band. (x, y, z) axes used for the assignment of orbitals are taken locally at the iron site. (a, b, c) axes are those of the orthorhombic unit cell with 20 atoms. 29
30 Fig. 9. LDA and GGA relative enthalpies of configuration 0 with respect to the aggregation of MgSiO 3 and FeSiO 3 : H = H(Mg Fe SiO 3 ) (0.875H(MgSiO 3 )+0.125H(FeSiO 3 )). Cusps in the lines are caused by spin transitions in Mg Fe SiO 3 or in FeSiO 3. Relative enthalpies of other configurations are intermediate values between blue and red lines. Horizontal dotted lines denote T S conf values in Rydberg at several temperatures, where S conf = k B (x log x + (1 x) log(1 x)), x = (see text). The mantle geotherm was derived by Brown and Shankland [1981]. 30
31 Fig. 10. Spin transition through mixed spin state from the HS to the LS states for configurations 0 and 11 for x = n is the LS iron fraction. Figure for GGA configuration 0 is omitted because n is 0 in this pressure and temperature range. Dashed lines denote a mantle geotherm derived by Brown and Shankland [1981]. 31
Spin crossovers in the Earth mantle. Spin crossovers in the Earth mantle
Spin crossovers in the Earth mantle Spin crossovers in the Earth mantle Renata M. Wentzcovitch Dept. of Chemical Engineering and Materials Science Minnesota Supercomputing Institute Collaborators Han Hsu
More informationarxiv: v1 [cond-mat.mtrl-sci] 24 Mar 2015
Iron spin crossover and its influence on post-perovskite transitions in MgSiO 3 and MgGeO 3 arxiv:1503.07194v1 [cond-mat.mtrl-sci] 24 Mar 2015 Gaurav Shukla a,, Mehmet Topsakal b, Renata M. Wentzcovitch
More informationPressure induced high spin to low spin transition in magnesiowüstite
Original Paper phys. stat. sol. (b) 243, No. 9, 2111 2116 (2006) / DOI 10.1002/pssb.200666814 Pressure induced high spin to low spin transition in magnesiowüstite Taku Tsuchiya 1, Renata M. Wentzcovitch
More informationThis article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution
More informationMulti-disciplinary Impact of the Deep Mantle Postperovskite
Multi-disciplinary Impact of the Deep Mantle Postperovskite Phase Transition Thorne Lay 1 Dion Heinz 2 Miaki Ishii 3 Sang-Heon Shim 4 Jun Tsuchiya 5 Taku Tsuchiya 5 Renata Wentzcovitch 5 David Yuen 6 1
More informationDetermination of the hyperfine parameters of iron in aluminous (Mg,Fe)SiO 3 perovskite
Determination of the hyperfine parameters of iron in aluminous (Mg,Fe)SiO 3 perovskite Jennifer M. Jackson Seismological Laboratory, Geological & Planetary Sciences California Institute of Technology VLab
More informationARTICLE IN PRESS. Received 26 April 2004; received in revised form 28 April 2004; accepted 11 May 2004 Available online
Earth and Planetary Science Letters xx (2004) xxx xxx www.elsevier.com/locate/epsl Phase transition in MgSiO 3 perovskite in the earth s lower mantle Taku Tsuchiya*, Jun Tsuchiya, Koichiro Umemoto, Renata
More informationIs the spin transition in Fe 2+ bearing perovskite visible in seismology?
Click Here for Full Article GEOPHYSICAL RESEARCH LETTERS, VOL. 37,, doi:10.1029/2010gl043320, 2010 Is the spin transition in Fe 2+ bearing perovskite visible in seismology? Razvan Caracas, 1 David Mainprice,
More informationComputational support for a pyrolitic lower mantle containing ferric iron
SUPPLEMENTARY INFORMATION DOI: 1.138/NGEO2458 Computational support for a pyrolitic lower mantle containing ferric iron Xianlong Wang, Taku Tsuchiya and Atsushi Hase NATURE GEOSCIENCE www.nature.com/naturegeoscience
More informationAnomalous thermodynamics properties in. ferropericlase throughout its spin crossover transition
1 Anomalous thermodynamics properties in ferropericlase throughout its spin crossover transition Z. Wu, 1,2 J. F. Justo, 1,2,3 C. R. S. da Silva, 2 S. de Gironcoli, 4,5 and R. M. Wentzcovitch 1,2 1 epartment
More informationresearch papers Theoretical determination of the structures of CaSiO 3 perovskites 1. Introduction Razvan Caracas* and Renata M.
Acta Crystallographica Section B Structural Science ISSN 0108-7681 Theoretical determination of the structures of CaSiO 3 perovskites Razvan Caracas* and Renata M. Wentzcovitch University of Minnesota,
More informationSupplementary Information
Supplementary Information Materials and Experiments 57 Fe-enriched enstatite sample [(Mg 0.6,Fe 0.4 )SiO 3 ] was synthesized by mixing powders of the oxides SiO 2, MgO, and 57 Fe 2 O 3 (90% enrichment
More informationElastic anomalies in a spin-crossover system: ferropericlase at lower. mantle conditions
Elastic anomalies in a spin-crossover system: ferropericlase at lower mantle conditions Zhongqing Wu, 1,2,3 João F. Justo, 1,4 and Renata M. Wentzcovitch 1,5,* 1 Department of Chemical Engineering and
More informationHigh-pressure, temperature elasticity of Fe- and Al-bearing MgSiO 3 : implications for the Earth s lower mantle. Abstract
High-pressure, temperature elasticity of Fe- and Al-bearing MgSiO 3 : implications for the Earth s lower mantle Shuai Zhang a,*, Sanne Cottaar b, Tao Liu c, Stephen Stackhouse c, Burkhard Militzer a,d
More informationdoi: /nature09940
LETTER doi:10.1038/nature09940 Spin crossover and iron-rich silicate melt in the Earth s deep mantle Ryuichi Nomura 1,2, Haruka Ozawa 1,3, Shigehiko Tateno 1, Kei Hirose 1,3, John Hernlund 4, Shunsuke
More informationElectronic spin states of ferric and ferrous iron in the lower-mantle silicate perovskite
American Mineralogist, Volume 97, pages 59 597, 01 Electronic spin states of ferric and ferrous iron in the lower-mantle silicate perovskite Jung-Fu Lin, 1, * Ercan E. Alp, Zhu Mao, 1 Toru Inoue, 3 Catherine
More informationOn Dynamic and Elastic Stability of Lanthanum Carbide
Journal of Physics: Conference Series On Dynamic and Elastic Stability of Lanthanum Carbide To cite this article: B D Sahoo et al 212 J. Phys.: Conf. Ser. 377 1287 Recent citations - Theoretical prediction
More informationarxiv:cond-mat/ v1 [cond-mat.mtrl-sci] 14 Jul 1997
Inverse versus Normal NiAs Structures as High Pressure Phases of FeO and MnO arxiv:cond-mat/9707139v1 [cond-mat.mtrl-sci] 14 Jul 1997 Z. Fang, K. Terakura, H. Sawada, T. Miyazaki & I. Solovyev JRCAT, Angstrom
More informationEarth and Planetary Science Letters
Earth and Planetary Science Letters 434 (2016) 264 273 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl High-pressure, temperature elasticity of
More informationPost-perovskite 1. Galley Proofs
16 September 2005 21:39 YB061180.tex McGraw Hill YB of Science & Technology Keystroked: 29/08/2005 Initial MS Page Sequence Stamp: 02350 Article Title: Post-perovskite Article ID: YB061180 1st Classification
More informationPost-stishovite transition in hydrous aluminous SiO 2 MN 55455, USA. Meguro-ku, Tokyo , Japan
1 Post-stishovite transition in hydrous aluminous SiO 2 Koichiro Umemoto 1,2, Katsuyuki Kawamura, 3 and Kei Hirose 2,4,5, and Renata M. Wentzcovitch 2,6,7 1 Department of Earth Sciences, University of
More informationarxiv: v1 [cond-mat.mtrl-sci] 13 Jan 2015
Spin crossover in ferropericlase from first-principles molecular dynamics E. Holmström and L. Stixrude Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK (Dated:
More informationAn Introduction to Post-Perovskite: The Last Mantle Phase Transition
An Introduction to Post-Perovskite: The Last Mantle Phase Transition Kei Hirose 1, John Brodholt 2, Thorne Lay 3, and David A. Yuen 4 Discovery of the perovskite to post-perovskite phase transition in
More informationGeophysical Journal International
Geophysical Journal International Geophys. J. Int. (2014) 197, 910 919 Advance Access publication 2014 February 27 doi: 10.1093/gji/ggu045 Effect of Fe-enrichment on seismic properties of perovskite and
More informationEarth and Planetary Science Letters
Earth and Planetary Science Letters 309 (2011) 179 184 Contents lists available at ScienceDirect Earth and Planetary Science Letters journal homepage: www.elsevier.com/locate/epsl Iron-rich perovskite
More informationThermal elasticity of (Fe x,mg 1 x ) 2 SiO 4 olivine and wadsleyite
GEOPHYSICAL RESEARCH LETTERS, VOL. 40, 290 294, doi:10.1002/grl.50131, 2013 Thermal elasticity of (Fe x,mg 1 x ) 2 SiO 4 olivine and wadsleyite M. Núñez-Valdez, 1 Z. Wu, 2 Y. G. Yu, 3 and R. M. Wentzcovitch
More informationDefects, Diffusion, Deformation and Thermal Conductivity in the Lower Mantle and D
Defects, Diffusion, Deformation and Thermal Conductivity in the Lower Mantle and D John Brodholt UCL Thanks to: Michael Ammann, Simon Hunt, James Wookey, Kai Wang, Andrew Walker and David Dobson College
More informationPBS: FROM SOLIDS TO CLUSTERS
PBS: FROM SOLIDS TO CLUSTERS E. HOFFMANN AND P. ENTEL Theoretische Tieftemperaturphysik Gerhard-Mercator-Universität Duisburg, Lotharstraße 1 47048 Duisburg, Germany Semiconducting nanocrystallites like
More informationThis article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution
More informationIron Partitioning between Ferropericlase and Bridgmanite in the Earth s Lower Mantle
Iron Partitioning between Ferropericlase and Bridgmanite in the Earth s Lower Mantle Shenzhen Xu 1, Jung-Fu Lin 2,3, and Dane Morgan 1,4 1 Materials Science Program, University of Wisconsin- Madison, Madison,
More informationAb initio molecular dynamics study of CaSiO 3 perovskite at P-T conditions of Earth s lower mantle
PHYSICAL REVIEW B 73, 184106 2006 Ab initio molecular dynamics study of CaSiO 3 perovskite at P-T conditions of Earth s lower mantle Donat J. Adams* and Artem R. Oganov Laboratory of Crystallography, Department
More informationα phase In the lower mantle, dominant mineralogy is perovskite [(Mg,Fe)SiO 3 ] The pyrolite mantle consists of: 60% olivine and 40% pyroxene.
Summary of Dan Shim s lecture on 3/1/05 Phase transitions in the Earth s mantle In this lecture, we focused on phase transitions associated with the transition zone 1. 410 km alpha olivine beta wadsleyite
More informationElasticity of single crystal and polycrystalline MgSiO 3 perovskite by Brillouin spectroscopy
GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L06620, doi:10.1029/2004gl019559, 2004 Elasticity of single crystal and polycrystalline MgSiO 3 perovskite by Brillouin spectroscopy Stanislav V. Sinogeikin Department
More informationAb initio elasticity and thermal equation of state of MgSiO 3 perovskite
Earth and Planetary Science Letters 184 (2001) 555^560 Express Letter www.elsevier.com/locate/epsl Ab initio elasticity and thermal equation of state of MgSiO 3 perovskite Artem R. Oganov *, John P. Brodholt,
More informationChemical Composition of the Lower Mantle: Constraints from Elasticity. Motohiko Murakami Tohoku University
Chemical Composition of the Lower Mantle: Constraints from Elasticity Motohiko Murakami Tohoku University Acknowledgements Jay D. Bass (University of Illinois) Stanislav V. Sinogeikin (University of Illinois)
More informationChemical Dynamics of the First Proton Coupled Electron Transfer of Water Oxidation on TiO 2 Anatase
Supplementary Information Chemical Dynamics of the First Proton Coupled Electron Transfer of Water Oxidation on TiO 2 Anatase Jia Chen, Ye-Fei Li, Patrick Sit, and Annabella Selloni Department of Chemistry,
More informationOctahedral tilting evolution and phase transition in orthorhombic NaMgF 3 perovskite under pressure
GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L04304, doi:10.1029/2004gl022068, 2005 Octahedral tilting evolution and phase transition in orthorhombic NaMgF 3 perovskite under pressure H.-Z. Liu, 1,2 J. Chen,
More informationModeling the Properties of Quartz with Clusters. Abstract
Modeling the Properties of Quartz with Clusters James R. Chelikowsky Department of Chemical Engineering and Materials Science Minnesota Supercomputer Institute University of Minnesota, Minneapolis, MN
More informationYuan Ping 1,2,3*, Robert J. Nielsen 1,2, William A. Goddard III 1,2*
Supporting Information for the Reaction Mechanism with Free Energy Barriers at Constant Potentials for the Oxygen Evolution Reaction at the IrO2 (110) Surface Yuan Ping 1,2,3*, Robert J. Nielsen 1,2, William
More informationLi ion migration in Li 3 PO 4 electrolytes: Effects of O vacancies and N substitutions. Winston-Salem, North Carolina 27106, USA
75 Downloaded 22 Dec 28 to 52.7.52.46. Redistribution subject to ECS license or copyright; see http://www.ecsdl.org/terms_use.jsp ECS Transactions, 3 (26) 75-82 (28).49/.35379 The Electrochemical Society
More informationSUPPLEMENTARY INFORMATION
DOI: 10.1038/NCHEM.1497 Stability of xenon oxides at high pressures Qiang Zhu, 1, a) Daniel Y. Jung, 2 Artem R. Oganov, 1, 3, b) Colin W. Glass, 4 Carlo Gatti, 5 and Andriy O. Lyakhov 1 1) Department of
More informationPhase Transitions in the Lowermost Mantle
Phase Transitions in the Lowermost Mantle S.-H. Dan Shim 1, B. Grocholski 2, K. Catalli 3, and V. Prakapenka 4 1 Arizona State University, 2 Smithsonian Institution, 3 Livermore National Lab 4 University
More informationSingle-Layer Tl 2 O: A Metal-Shrouded 2D Semiconductor with High Electronic Mobility
Supporting information for Single-Layer Tl 2 O: A Metal-Shrouded 2D Semiconductor with High Electronic Mobility Yandong Ma, Agnieszka Kuc, and Thomas Heine*, Wilhelm-Ostwald-Institut für Physikalische
More informationSupporting Information. Intrinsic Lead Ion Emissions in Zero-dimensional Cs 4 PbBr 6 Nanocrystals
Supporting Information Intrinsic Lead Ion Emissions in Zero-dimensional Cs 4 PbBr 6 Nanocrystals Jun Yin, 1 Yuhai Zhang, 1 Annalisa Bruno, 2 Cesare Soci, 2 Osman M. Bakr, 1 Jean-Luc Brédas, 3,* Omar F.
More informationHigh-temperature structural phase transitions in perovskite (CaTiO 3 )
J. Phys.: Condens. Matter 8 (1996) 8267 8275. Printed in the UK High-temperature structural phase transitions in perovskite (CaTiO 3 ) Simon A T Redfern Department of Earth Sciences, University of Cambridge,
More informationAmerican Mineralogist, Volume 84, pages , Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR U.K.
American Mineralogist, Volume 84, pages 214 220, 1999 High-resolution synchrotron X-ray powder diffraction and Rietveld structure refinement of two (Mg 0.95,Fe 0.05 )SiO 3 perovskite samples synthesized
More informationLow-spin Fe in silicate perovskite and a possible layer at the base of the lower mantle
Low-spin Fe in silicate perovskite and a possible layer at the base of the lower mantle C. Mccammon, L. Dubrovinsky, O. Narygina, I. Kantor, X. Wu, K. Glazyrin, I. Sergueev, A.I. Chumakov To cite this
More informationMAGNETIC COLLAPSE AND THE BEHAVIOR OF TRANSITION METAL OXIDES: FeO AT HIGH PRESSURES
MAGNETIC COLLAPSE AND THE BEHAVIOR OF TRANSITION METAL OXIDES: FeO AT HIGH PRESSURES R. E. COHEN, Y. FEI, R. DOWNS **, I. I. MAZIN *** ; D. G. ISAAK **** * Carnegie Institution of Washington, 5251 Broad
More informationSpin states of iron impurities in magnesium oxide under pressure: a possible intermediate state. Abstract
Spin states of iron impurities in magnesium oxide under pressure: a possible intermediate state R. Larico (1), L. V. C. Assali (2), and J. F. Justo (1) (1) Escola Politécnica, Universidade de São Paulo,
More informationUniversity of Chinese Academy of Sciences, Beijing , People s Republic of China,
SiC 2 Siligraphene and Nanotubes: Novel Donor Materials in Excitonic Solar Cell Liu-Jiang Zhou,, Yong-Fan Zhang, Li-Ming Wu *, State Key Laboratory of Structural Chemistry, Fujian Institute of Research
More informationFirst Principle Calculation of Electronic, Optical Properties and Photocatalytic Potential of CuO Surfaces
ICoSE Conference on Instrumentation, Environment and Renewable Energy (2015), Volume 2016 Conference Paper First Principle Calculation of Electronic, Optical Properties and Photocatalytic Potential of
More informationSUPPLEMENTARY INFORMATION
Supplementary Methods Materials Synthesis The In 4 Se 3-δ crystal ingots were grown by the Bridgeman method. The In and Se elements were placed in an evacuated quartz ampoule with an excess of In (5-10
More informationSUPPLEMENTARY INFORMATION
SUPPLEMENTARY INFORMATION doi:10.1038/nature11294 Review of previous works on deep-liquid properties The major parameters controlling the buoyancy of deep-mantle melts are (i) the changes in atomic packing
More informationLaboratory Electrical Conductivity Measurement of Mantle Minerals
Laboratory Electrical Conductivity Measurement of Mantle Minerals Takashi Yoshino Institute for Study of the Earth s Interior, Okayama University Outline 1. Brief introduction 2. Conduction mechanisms
More informationSharpness of the D 00 discontinuity beneath the Cocos Plate: Implications for the perovskite to post-perovskite phase transition
Click Here for Full Article GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L03304, doi:10.1029/2007gl032465, 2008 Sharpness of the D 00 discontinuity beneath the Cocos Plate: Implications for the perovskite to
More informationDefects in TiO 2 Crystals
, March 13-15, 2013, Hong Kong Defects in TiO 2 Crystals Richard Rivera, Arvids Stashans 1 Abstract-TiO 2 crystals, anatase and rutile, have been studied using Density Functional Theory (DFT) and the Generalized
More informationThe high pressure electronic spin transition in iron: Potential impacts upon mantle mixing
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116,, doi:10.1029/2010jb007965, 2011 The high pressure electronic spin transition in iron: Potential impacts upon mantle mixing M. H. Shahnas, 1 W. R. Peltier, 1 Z.
More informationCh 6: Internal Constitution of the Earth
Ch 6: Internal Constitution of the Earth Mantle composition Geological background 88 elements found in the Earth's crust -- of these, only 8 make up 98%: oxygen, silicon, aluminum, iron, calcium, magnesium,
More informationGrowth Mechanism of Hexagonal Shape Graphene Flakes with Zigzag Edges. Johnson, *
Growth Mechanism of Hexagonal Shape Graphene Flakes with Zigzag Edges Zhengtang Luo, Seungchul Kim, Nicole Kawamoto, Andrew M. Rappe, and A.T. Charlie Johnson, * Department of Physics and Astronomy, University
More informationStrong Facet-Induced and Light-Controlled Room-Temperature. Ferromagnetism in Semiconducting β-fesi 2 Nanocubes
Supporting Information for Manuscript Strong Facet-Induced and Light-Controlled Room-Temperature Ferromagnetism in Semiconducting β-fesi 2 Nanocubes Zhiqiang He, Shijie Xiong, Shuyi Wu, Xiaobin Zhu, Ming
More informationThe primitive nature of large low shear-wave velocity provinces
The primitive nature of large low shear-wave velocity provinces Frédéric Deschamps 1, Laura Cobden 3, and Paul J. Tackley 2 1 Institute of Earth Sciences, Academia Sinica, 128 Academia Road Sec. 2, Nangang,
More informationPOST-PEROVSKITE MGSIO 3 INVESTIGATED BY FIRST PRINCIPLES
1 POST-PEROVSKITE MGSIO 3 INVESTIGATED BY FIRST PRINCIPLES TAKU TSUCHIYA 1, JUN TSUCHIYA 1, AND RENATA M. WENTZCOVITCH Chemical Engineering and Materials Science, Minnesota Supercomputing Institute for
More informationZhu Mao. Department of Geological Sciences The University of Texas at Austin Austin, TX
Zhu Mao Department of Geological Sciences The University of Texas at Austin Austin, TX 78712 310-341-9655 zhumao@mail.utexas.edu Education: Princeton University Ph.D. Gepphysics 2009 M.S. Geophysics 2006
More informationEarth and Planetary Science Letters
Earth and Planetary Science Letters 417 (2015) 57 66 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Spin state transition and partitioning of
More informationElectronic structure of solid FeO at high pressures by quantum Monte Carlo methods
Physics Procedia 3 (2010) 1437 1441 www.elsevier.com/locate/procedia Electronic structure of solid FeO at high pressures by quantum Monte Carlo methods Jindřich Kolorenč a and Lubos Mitas a a Department
More informationSelf-compensating incorporation of Mn in Ga 1 x Mn x As
Self-compensating incorporation of Mn in Ga 1 x Mn x As arxiv:cond-mat/0201131v1 [cond-mat.mtrl-sci] 9 Jan 2002 J. Mašek and F. Máca Institute of Physics, Academy of Sciences of the CR CZ-182 21 Praha
More informationAuthor(s) Togo, Atsushi; Oba, Fumiyasu; Tanak. Citation PHYSICAL REVIEW B (2008), 78(13)
Title First-principles calculations of th between rutile-type and CaCl-type Author(s) Togo, Atsushi; Oba, Fumiyasu; Tanak Citation PHYSICAL REVIEW B (8), 78(3) Issue Date 8- URL http://hdl.handle.net/433/8463
More informationSupplementary Figure 1 Two-dimensional map of the spin-orbit coupling correction to the scalar-relativistic DFT/LDA band gap. The calculations were
Supplementary Figure 1 Two-dimensional map of the spin-orbit coupling correction to the scalar-relativistic DFT/LDA band gap. The calculations were performed for the Platonic model of PbI 3 -based perovskites
More informationAmerican Mineralogist, Volume 102, pages , 2017
American Mineralogist, Volume 102, pages 357 368, 2017 Equation of state and hyperfine parameters of high-spin bridgmanite in the Earth s lower mantle by synchrotron X-ray diffraction and Mössbauer spectroscopy
More informationPhysics of the Earth and Planetary Interiors
Physics of the Earth and Planetary Interiors 177 (2009) 103 115 Contents lists available at ScienceDirect Physics of the Earth and Planetary Interiors journal homepage: www.elsevier.com/locate/pepi Structure
More information* Theoretische Physik II, Universitat Dortmund, Dortmund, Germany
JOURNAL DE PHYSIQUE IV Colloque C8, suppl6ment au Journal de Physique III, Volume 5, dkembre 1995 Structural Phase Transformation and Phonon Softening in Iron-Based Alloys H.C. Herper, E. Hoffmann, P.
More informationEquation of state of the postperovskite phase synthesized from a natural (Mg,Fe)SiO 3 orthopyroxene
Equation of state of the postperovskite phase synthesized from a natural (Mg,Fe)SiO 3 orthopyroxene Sean R. Shieh*, Thomas S. Duffy, Atsushi Kubo, Guoyin Shen, Vitali B. Prakapenka, Nagayoshi Sata, Kei
More informationFirst-principles studies of the structural, electronic, and optical properties of a novel thorium compound Rb 2 Th 7 Se 15
First-principles studies of the structural, electronic, and optical properties of a novel thorium compound Rb 2 Th 7 Se 15 M.G. Brik 1 Institute of Physics, University of Tartu, Riia 142, Tartu 5114, Estonia
More informationDFT calculation of pressure induced phase transition in silicon
DFT calculation of pressure induced phase transition in silicon Michael Scherbela scherbela@student.tugraz.at 2015-12-07 Contents 1 Introduction 2 2 Structure of the input file 2 3 Calculation of phase
More informationARTICLE IN PRESS. Received 8 August 2004; received in revised form 25 October 2004; accepted 23 November 2004 Editor: B. Wood
DTD 5 Earth and Planetary Science Letters xx (2004) xxx xxx www.elsevier.com/locate/epsl The effect of temperature on the seismic anisotropy of the perovskite and post-perovskite polymorphs of MgSiO 3
More informationSynthesis and crystal chemistry of Fe 3+ -bearing (Mg,Fe 3+ )(Si,Fe 3+ )O 3 perovskite
American Mineralogist, Volume 97, pages 1915 1921, 2012 Synthesis and crystal chemistry of Fe -bearing (Mg,Fe )(Si,Fe )O 3 perovskite Daniel R. Hummer* and Yingwei Fei Geophysical Laboratory, Carnegie
More informationSCIENCE CHINA Physics, Mechanics & Astronomy. Electronic structure and optical properties of N-Zn co-doped -Ga 2 O 3
SCIENCE CHINA Physics, Mechanics & Astronomy Article April 2012 Vol.55 No.4: 654 659 doi: 10.1007/s11433-012-4686-9 Electronic structure and optical properties of N-Zn co-doped -Ga 2 O 3 YAN JinLiang *
More informationElectronic structure, magnetism, and optical properties of Fe 2 SiO 4 fayalite at ambient and high pressures: A GGA U study
Electronic structure, magnetism, and optical properties of Fe 2 SiO 4 fayalite at ambient and high pressures: A GGA U study Xuefan Jiang 1,2, * and G. Y. Guo 1,3, 1 Department of Physics, National Taiwan
More informationarxiv:cond-mat/ v1 5 Nov 2003
On-surface and Subsurface Adsorption of Oxygen on Stepped Ag(210) and Ag(410) Surfaces A. Kokalj a,b, N. Bonini a, A. Dal Corso a, S. de Gironcoli a and S. Baroni a arxiv:cond-mat/0311093v1 5 Nov 2003
More informationEffects of substitutions of C atoms by Al and N in the w-aln compound
Journal of Physics: Conference Series PAPER OPEN ACCESS Effects of substitutions of C atoms by Al and N in the w-aln compound To cite this article: J F Murillo et al 2016 J. Phys.: Conf. Ser. 687 012114
More informationA COMPUTATIONAL INVESTIGATION OF MIGRATION ENTHALPIES AND ELECTRONIC STRUCTURE IN SrFeO 3-δ
A COMPUTATIONAL INVESTIGATION OF MIGRATION ENTHALPIES AND ELECTRONIC STRUCTURE IN SrFeO 3-δ A. Predith and G. Ceder Massachusetts Institute of Technology Department of Materials Science and Engineering
More informationAdaptive Genetic Algorithm for Crystal Structure Prediction
Adaptive Genetic Algorithm for Crystal Structure Prediction S Q Wu 1,2, M Ji 2, C Z Wang 2,, M C Nguyen 2, X Zhao 2, K Umemoto 2,3, R M Wentzcovitch 4 and K M Ho 2, 1 Department of Physics, Xiamen University,
More informationInsulating states of LiBeH 3 under extreme compression
PHYSICAL REVIEW B 79, 134116 29 Insulating states of LiBeH 3 under extreme compression Chao-Hao Hu, 1, * Artem R. Oganov, 2,3 Andriy O. Lyakhov, 2 Huai-Ying Zhou, 1 and J. Hafner 4 1 Department of Information
More informationAnisotropy of Earth s D layer and stacking faults in MgSiO 3 post-perovskite
1 Anisotropy of Earth s D layer and stacking faults in MgSiO 3 post-perovskite Artem R. Oganov 1*, Roman Martoňák 2, Alessandro Laio 2, Paolo Raiteri 2, Michele Parrinello 2 1 Laboratory of Crystallography,
More informationRe-evaluating CeO 2 Expansion Upon Reduction: Non-counterpoised Forces, Not Ionic Radius Effects, are the Cause
Re-evaluating CeO 2 Expansion Upon Reduction: Non-counterpoised Forces, Not Ionic Radius Effects, are the Cause Christopher L. Muhich, a* a ETH Zurich, Department of Mechanical and Process Engineering,
More informationSupporting Information
Supporting Information Tsuchiya and Tsuchiya 10.1073/pnas.1013594108 SI Text Structure Models for Ultrahigh-Pressure Phase of SiO 2 and Other Compounds. We examined initially 15 different potential structure
More informationSupporting Information
Supporting Information Interaction between Single Noble Metal Atom and Graphene Edge: A Study via Aberration-corrected Transmission Electron Microscopy METHODS Preparing Monolayer Graphene with Free Edges.
More informationA BADER S TOPOLOGICAL APPROACH FOR THE CHARACTERIZATION OF PRESSURE INDUCED PHASE TRANSITIONS
A BADER S TOPOLOGICAL APPROACH FOR THE CHARACTERIZATION OF PRESSURE INDUCED PHASE TRANSITIONS FILIPPO PARISI Dipartimento di Matematica e Geoscienze, Università di Trieste, Via E. Weiss 2, 34128 Trieste,
More informationEarth and Planetary Science Letters
Earth and Planetary Science Letters 357-358 (2012) 130 136 Contents lists available at SciVerse ScienceDirect Earth and Planetary Science Letters journal homepage: www.elsevier.com/locate/epsl Radiative
More informationSnO 2 Physical and Chemical Properties due to the Impurity Doping
, March 13-15, 2013, Hong Kong SnO 2 Physical and Chemical Properties due to the Impurity Doping Richard Rivera, Freddy Marcillo, Washington Chamba, Patricio Puchaicela, Arvids Stashans Abstract First-principles
More informationStability of MgSiO, Perovskite in the Lower Mantle
Stability of MgSiO, Perovskite in the Lower Mantle Sang-Heon Shim Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts As it is expected
More informationA synchrotron Mössbauer spectroscopy study of (Mg,Fe)SiO 3 perovskite up to 120 GPa
American Mineralogist, Volume 90, pages 99 05, 005 A synchrotron Mössbauer spectroscopy study of (Mg,Fe)SiO 3 perovskite up to 0 GPa JENNIFER M. JACKSON,, * WOLFGANG STURHAHN, GUOYIN SHEN, 3 JIYONG ZHAO,
More informationCitation for published version (APA): Sadoc, A. G. J. (2008). Charge disproportionation in transition metal oxides s.n.
University of Groningen Charge disproportionation in transition metal oxides Sadoc, Aymeric Gaël Jocelyn IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish
More informationFirst-principles calculations of bulk and interfacial thermodynamic properties for fcc-based Al-Sc alloys
PHYSICAL REVIEW B VOLUME 57, NUMBER 18 1 MAY 1998-II First-principles calculations of bulk and interfacial thermodynamic properties for fcc-based Al-Sc alloys Mark Asta, S. M. Foiles, and A. A. Quong*
More informationHydrogenation of Penta-Graphene Leads to Unexpected Large. Improvement in Thermal Conductivity
Supplementary information for Hydrogenation of Penta-Graphene Leads to Unexpected Large Improvement in Thermal Conductivity Xufei Wu, a Vikas Varshney, b,c Jonghoon Lee, b,c Teng Zhang, a Jennifer L. Wohlwend,
More informationCHAPTER 6. ELECTRONIC AND MAGNETIC STRUCTURE OF ZINC-BLENDE TYPE CaX (X = P, As and Sb) COMPOUNDS
143 CHAPTER 6 ELECTRONIC AND MAGNETIC STRUCTURE OF ZINC-BLENDE TYPE CaX (X = P, As and Sb) COMPOUNDS 6.1 INTRODUCTION Almost the complete search for possible magnetic materials has been performed utilizing
More informationStructural and Electronic Effects on the Properties of Fe 2 (dobdc) upon Oxidation with N 2 O
Supporting information for paper in Inorganic Chemistry, April 11, 016, page S-1 Structural and Electronic Effects on the Properties of Fe (dobdc) upon Oxidation with N O oshua Borycz, 1, oachim Paier,
More informationTRICRITICAL POINTS AND LIQUID-SOLID CRITICAL LINES
TRICRITICAL POINTS AND LIQUID-SOLID CRITICAL LINES ANNELI AITTA Institute of Theoretical Geophysics, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road
More informationTradeoffs in chemical and thermal variations in the post-perovskite phase transition: Mixed phase regions in the deep lower mantle?
Physics of the Earth and Planetary Interiors 159 (2006) 24 246 Tradeoffs in chemical and thermal variations in the post-perovskite phase transition: Mixed phase regions in the deep lower mantle? Frank
More informationGeos 306, Mineralogy Final Exam, Dec 12, pts
Name: Geos 306, Mineralogy Final Exam, Dec 12, 2014 200 pts 1. (9 pts) What are the 4 most abundant elements found in the Earth and what are their atomic abundances? Create a reasonable hypothetical charge-balanced
More information