Theoretical simulation of Nanoclustersm (2)

Transcription

1 Theoretical simulation of Nanoclustersm (2) Xiaohu Yu Moscow Institute of Physics and Technology

2 Contents Introduction of clusters and theoretical methods The stability and geometric structure of different clusters Design the different superatoms Conclusion

3 Introduction Clusters: a bridge across disciplines Clusters: an embryomnic form of matters Clusters: made by laboratory, often metastable, composition can change Molecule: made by nature, belong clusters Superatom: unique stability and properties of clusters, building blocks

4 Theoretical Methods Quantum chemical approach Density functional theory Genetic program Basin hopping method Evolutionary program

5 Superatom and magic number Shiv Khanna 1992, superatom Jellium model Octet rule 18 electron rule Wade-Mingos rule Superhalogen Superalkali Puru Jena J. Phys.Chem. Lett.4(2013) 1432

6 Weakly interaction cluster 1981,Echt and coworkers a mass spectrum of xenon, N = 1+ (10p 2 +2) Noble gas atom exhibit stability at 13, 55, 147. Atomic shell closure

7 8-e rule

8 18-e rule Transition metal carbonyl 18 electron rule

9 1984, Knight and coworkers Jellium model

10 Alkali metals 1984 Knight and coworkers Magic number 2,8,20,40,58,and 92 1s 2, 1p 6,1d 10,2s 2,1f 14,2p 6, 1g 18. Na cation clusters should be 3, 9, 21, 41, 59,93 Odd-even alternation (Jahn-Teller effect) The similarity between magic numbers in nuclei and atomic clusters Bridge nuclear and condensed-matter physics Electronic shell closure Na J. Chem. Phys. 123(2005)

11 Alkali-earth metal clusters Be J. Chem. Phys. 123(2005) Shell closure effects: 2, 8, 20, 34, 40

12 Al cluster superatoms Al 13 cluster behave like a halogen atom Al 14 cluster exhibits properties analogous to alkaline earth atom Bergeron et al. Science 307(2005) 231

13 Multiple valence superatoms Al 13 cluster behave like a halogen atom Al 14 cluster exhibits properties analogous to alkaline earth atom Al 7- exhibits multiple valence Reveles et al. Natl. Acad. Sci. USA. 103(2006) 18405

14 Coinage metal clusters Cu, Ag, Au monovalent like alkali metal Stability like alkali metal The geometric structure is different with alkali Au unique Au J. Chem. Phys. 132 (2010)

15 Transition-metal clusters Ni Unfilled d-orbital Different structure with simple metals J. Phys. Chem. A, 1997, 101 (6), pp 1072

16 Semiconductor clusters Odd-even alternation at n<8 Odd cluster is more stable than even cluster Ring or cage is favored at more C atoms fullerene J. Chem. Phys. 87(1987); 2191

17 Semiconductor clusters Nature 1998;392:582

18 Bialloy clusters Al12Au20 J. Chem. Phys. 131(2009)

19 B x H y (borane) Wade-Mingos rule: stability of boranes requires (n+1) pairs of electrons, where n is the number of vortices of a boron polyhedron. Al x H y Polyhedral skeletal electron pair theory (PSEPT)

20 Ionically bonded cluster (MgO) x, (CaO) x, (NaCl) x and so on X=4, 13,22,37. One part of bulk J. Chem. Phys. 106(1997), 2323

21 Superhalogen EA (electron affinity) of Cl, 3.62 ev Bartlett and Lohmann PtF , Gutsev and Boldyrev showed a central metal atom decorating with halogen ligands (coined superhalogen) Gutsev et al. Chem. Phys. 56(1981) 277 Gutsev et al. Chem. Phys. Lett. 92(1982) 262

22 Mn-based magnetic superhalogens Mn n Cl 2n+1- stabilize by superhalogen Not by electronic shell closure or atomic shell closure Mn 2+ and high-spin d 5 configuration, extra electron localizes 3Cl, high EA (5 ev>3.62 ev Cl) Wu et al. Angew.Chem.Int.Ed.2001,50,

23 Hyperhalogen The peripheral halogen atoms replace by superhalogen molieties. Willis et al. Angew. Chem. Int. Ed. 2010, 49,

24 Superalkali Ionization potentials (IPs) of alkali metal ( ev) 1981, Gutsev and Boldyrev Superalkali: ionization potentials (IPs) lower than 3.9 ev(cesium) Formulation of superalkali ML k+n Gutsev et al. Chem. Phys. 56(1981) 277 Gutsev et al. Chem. Phys. Lett. 92(1982) 262

25 Superalkali Lower ionization potentials (IPs) than alkali metal atoms ( ev). Sun et al. Inorg. Chem. 53 (2014) 6170

26 Design Superalkali cations Lower the electron affinity by halogenation Hou et al. J. Am.Chem.Soc. 136 (2014) 2921

27 Aromatic Superatoms Aromatic superalkali cations by replacing the atomic M cores with aromatic anions J. Phys.Chem. C 117(2013) 24618

28 Designer magnetic superatoms Doping simple metal clusters with magnetic atoms VNa 8 is magnetic superatom with a filled d-subshell and a magnetic moment (5 μ B ) Zhang et al. J. Am. Chem. Soc. 135(2013) 4856

29 Designer magnetic superatoms Magnetic superatoms can be designed by combinations of localized and delocalized electrons in the valence space of a cluster Reveles et al. Nat. Chem. 1(2009) 310

30 Hunt s rule in superatom The D states are split into a group of (D xy, D x2 - y2, D xz, and D yz ) and a D z2 state Fe has 4s 2 and 3d 6, Mg has 3S 2 Medel et al. Natl. Acad. Sci. USA. 108(2011)10062

31 S-P coupling induced unusual Open-shell metal clusters Al 5 Mg 2- and Al 11 Mg 3- have 20 and 40 e - (electronic shell closure) Al 2 Mg - clusters originate from S-P molecular orbital coupling Cheng et al. J. Am. Chem. Soc. 136(2014) 4821

32 Met-Cars Met-Cars (Metallocarbohedrynes) Ti 8 C 12 (Ti, Zr, Hf, V, and Nb, Cr, Mo, Fe) Science 255(1992) 1411

33 Conclusion Clusters: a bridge across disciplines The stability of nanocluster: magic number and superatoms Different kinds of clusters Design the superatoms