Refinement of the crystal structure of wollastonite-2m (parawollastonite)

Transcription

1 Zeitschrift fur Kristallographie 168, (1984) iq by R. Olden bourg Verlag, Munchen 1984 Refinement of the crystal structure of wollastonite-2m (parawollastonite) K.-F. Hesse Mineralogisches Institut, Universitat Kiel, D-2300 Kiel, Federal Republic of Germany Received: February 29, 1984 Crystal structure I Wollastonite-2M I Ca3[Si309] Abstract. The structure of wobastonite-2m from Death ValJey, CaJifornia, USA, Ca3[Si30g], is monoclinic with space group P21!a, a = (3), b=7.322(1), c=7.063(1)a, {3=95.30(2)', Z=4 and Dx=2.92g cm-3, and was refined to R (unweighted) =0.038 and R(weighted)=0.031 using 3886 nonequivalent reflections. WoBastonite-2M contains dreier single chains. Si-O distances vary between 1.580(2) and 1.664(2) A (mean A), Ca-O distances between 2.224(2) and 2.640(6) A (mean A). Introduction CaSi03 exists in two structuraljy quite different forms. The phase stable above ca C is a cyclosilicate caljed pseudowobastonite or (X-woBastonite, which contains rings of three corner-shared [Si04]tetrahedra. Depending on the stacking arrangement of the [Si30g]rings and cations a number of polytypes of pseudowobastonite have been described (Yamanaka and Mori, 1981). Below ca C CaSi03 contains dreier single chains, i. e. chains with three [Si04]tetrahedra in the repeat unit. A series of polytypes have been reported with different packing arrangements of the single chains (Wenk, 1969; Henmi et a!., 1983). These polytypes are caljed {3-wolJastonite or woljastonites and are distinguished by the symbols nt and nm, where T and M stands for triclinic and monoclinic symmetry of the polytype and n indicates the number of subcebs with dsubcell (100) c:::. 7.7 A in the unit cell of the polytype. The polytype 2M is often caljed parawoljastonite. In both series of polytypes (X-as web as {3-wolJastonite exist disordered phases. First X-ray studies of pseudowoljastonite have been carried out by Jeffery and HeBer (1953) and the structure has been determined by Yamanaka and Mori (1981).

2 Table 1. Positional and thermal parameters with standard deviations. The anisotropic temperature factors have the form exp - 2n2( Ull h2a*2 + U22k2b*2 + U33PC*2 + 2 U12hka*b* + 2 U13hla*c* +2 U23klb*c*). The standard deviations in parentheses refer to the last digit 0 -, ~~~on rl r; N x y Z U11 U22 U33 U23 U/3 Ul2 Ca(1) (0) (2) (0) (1) (1 ) (1) (4) (1) (2) Ca(2) (0) (6) (1 ) (2) (2) (1) (4) (1 ) (4) Ca(3) (0) (6) (1) (2) (5) (1) (3) (1) (3) SiC1) (0) (1 ) (1) (3) (4) (2) (2) (2) (2) Si(2) (0) (1) (1) (3) (4) (2) (2) (2) (2) 7\ Si(3) (0) (1) (1 ) (2) (2) (2) (3) (1) (3) ~0(1) (1) (8) (2) (5) (6) (5) (9) (4) (10) ::r: 0(2) (1) (8) (2) (5) (6) (5) (11) (4) (10) (1) on 0(3) (1) (16) (2) (6) (21) O.0065( 5) (10) (4) (11) on (1).. 0(4) (1) (15) (2) (6) (23 ) (5) (9) (4) (10) ṇ.., 0(5) (1) (15) (2) (6) (15) (7) (9) (5) (8) '<: on 0(6) (1) (13) (3) (6) (21) (7) (9) (5) (7) E- 0(7) (1) (3) (3) (9) (8) (7) (6) (6) (6) ~..., 0(8) (1) (3) (3) (9) (8) (7) (6) (6) (6) (') := 0(9) (1) (3) (2) (6) (5) (6) (8) (5) (8) a-..., (1)

3 "!""" ~:I: (1) '-0 Vl Table2. Bond lengths (A) and angles (D) compared ~n with corresponding values from Trojer (1968). The standard deviations in parentheses refer to the '" (1) '" last digit (J.., [Si04]tetrahedra (Trojer) o -O-distances o -Si -0 angles (Trojer) '< '". Si - 0 distances ;!;..., Si(l) -0(3) 1.608(3) 1.779(7) 0(3) -0(5) 2.736(2) 118.3(2) 12500' 2.., Si(l) -0(5) 1.580(2) 1.580(6) 0(3) - 0(7) 2.646(3) 108.7(2) 10830' (1) 0 Si(1) - 0(7) 1.648(2) 1.554(5) 0(3) - 0(9) 2.586(9) 105.3(4) , ' Si(l) -0(9) 1.643(2) 1.622(7) 0(5) -0(7) 2.697(3) 113.3(2) 10425' ~2-0(5) - 0(9) 2.587(8) 106.7(4) 10606' EO Mean (7) '" - 0(9) 2.576(3) 103.0(1) 10559' a Mean Mean g. (1) Si(2) -0(4) 1.619(3) 1.788(6) 0(4) -0(6) 2.730(2) 116.2(2) 12407' N ~Si(2)-0(6) 1.595(3) 1.577(6) 0(4) -0(8) 2.645(3) 108.0(2) 10834' Si(2) -0(8) 1.652(2) 1.558(6) 0(4)-0(9) 2.608(8) 106.2(4) 10408' Si(2) -0(9) 1.643(2) 1.626(6) O(6) - 0(8) 2.680(3) 111.3(2) ' 0(6) -0(9) 2.678(7) 111.6(3) 10900' Mean (8) -0(9) 2.570(3) 102.5(1) 10535' Mean Mean Si(3) -0(1) 1.606(2) 1.594(5) 0(1) -0(2) 2.811(2) 122.0(1) 12930' Si(3) -0(2) 1.606(2) 1.732(5) 0(1) -0(7) 2.547(4) 102.3(2) 9639' Si(3) -0(7) 1.665(2) 1.637(6) 0(1) -0(8) 2.568(4) 103.5(2) 9610' Si(3) -0(8) 1.662(2) 1.626(7) 0(2) - 0(7) 2.693(4) 110.9(2) 11217' 0(2) -0(8) 2.711(4) 112.1(2) 11213' Mean (7) -0(8) 2.625(3) 104.2(1) ' Mean Mean 109.2

4 Table 2. (Continued) [Ca06]polyhedra (Trojer) Ca - 0 distances Ca(1) -0(1) 2.339(2) 2.214(5) Ca(2) -0(1) Ca(1) -0(2) 2.426(2) 2.356(5) Ca(2) - 0(2) Ca(1) -0(3) 2.367(9) 2.392(8) Ca(2) -0(4) Ca(l) -0(3') 2.420(9) 2.445(9) Ca(2) -0(5) Ca(1) -0(4) 2.330(8) 2.396(9) Ca(2) -0(6) Ca(l) -0(4') 2.430(8) 2.407(9) Ca(2) - 0(8) Ca(l) -0(9) 2.640(6) Mean [Ca06] Mean Mean [CaO?] all other ~3.641 all other > (Trojer) (Trojer) 2.434(6) 2.494(8) Ca(3) -0(1) 2.429(6) 2.475(8) (8) 2.598(8) Ca(3) -0(2) 2.490(7) 2.545(8) (2) 2.174(5) Ca(3) - 0(3) 2.315(2) 2.168(5) 2.337(10) 2.318(13) Ca(3) -0(5) 2.233(9) 2.298(13) 2.224(9) 2.290(5) Ca(3) -0(6) 2.428(9) 2.415(12) 2.409(2) 2.537(6) Ca(3) -0(7) 2.413(2) 2.511(5) Mean all other ~3.253 Si Si angles (Trojer) Si(1) - 0(9) - Si(2) 150.2(1) 15148' Si(1) -0(7) -Si(3) 140.2(1) 13525' Si(2) - 0(8) - Si(3) 139.3(1) 13632' Mean 143.2

5 K.-F. Hesse: Crystal structure of wollastonite-2m 97 The structure of wollastonite-l T has been proposed by Dornberger-Schiff et al. (1954) and determined by Mamedov and Belov (1956), refined by Buerger and Prewitt (1961) and Ohashi and Finger (1978), that of wollastonite-2m by Tolliday (1958), and Trojer (1968). The structures of the higher polytypes 3T, 4T, STand 7T of wollastonite have been described by Henmi et al. (1983) and Henmi et ai. (1978). The aim of this refinement of wollastonite-2m is to comment on the large differences in Si -0 distances and 0 -Si -0 angles of Trojer's structure determination. Experimental A specimen of parawollastonite crystals from Death Valley, California, was kindly provided by H.-R. Wenk. A crystal measuring x x mm was used for data collection on an automatic Philips PW 1100 four-circle diffractometer with graphite-monochromatized MoKIX radiation (2 = ) and w - 2 e (emax= 500). The intensities of 9122 non-equivalent reflections were measured; 3886 of these had I> 3 a(i) and were implied in the subsequent refinement. The standard deviations, a(i), were estimated using the formula of Stout and Jensen (1968). Refined cell dimensions were determined with the program LA T written by Hornstra and Vossers (1973/74). Lorentz, polarization and absorption corrections (Busing et ai., 1957) were applied [/i(mokix)=24.56cm-1]. The structure was refined by full-matrix least-squares analysis with the program SHELX-76 (Sheldrick, 1976), starting with the atomic coordinates given by Trojer (1968). The atomic scattering factors were taken from the International Tables for X-ray Crystallography, VoL IV, 1974, for neutral atoms. Anisotropic refinements of the crystal structure converged at R (unweighted) = and R(weighted) =0.031 {R(weighted)=.rY;-OFol-IFcj]/.rY;-!Fo!, w= 1/a2}. Final atomic parameters are given in Table 1, bond lengths and angles in Table 2. A list of observed and calculated structure factors can be obtained from the author. Results In Table 2 the bond lengths d(si - 0) and d(ca - 0) and the bond angles o -Si -0 and Si -0 -Si obtained are compared with those reported by Trojer. The ranges ijd=dmax -dmin and ij 1: = 1:max-1':min obtained (0.084 A, A and 19.8 ) are considerably smaller than the corresponding ranges given by Trojer (0.234 A, A and 33.3 respectively) and indicate that the [Si04]tetrahedra and [Ca06]polyhedra are less distorted than reported.

6 98 K.-F. Hesse: Crystal structure of wollastonite-2m Acknowledgement. I thank H. H. Jensen for helpful technical assistance. Computations were carried out at the Rechenzentrum der Universitat Kiel. I thank H.-R. Wenk for supplying a sample of the Death Valley parawollastonite. A critical review of the manuscript by F. Liebau is appreciated. References Buerger, M. J., Prewitt, C. T.: The crystal structure of wollastonite and pectolite. Proc. Natl. Acad. Sci. 47, (1961) Busing, W. R., Levi, H. B.: High-speed computation of the absorption correction for single crystal diffraction measurements. Acta Crystallogr. 10, (1957) Domberger-Schiff, K., Liebau, F., Thilo, E.: Ober die Kristallstruktur des (NaAs03)" des Maddrellschen Salzes und des {i-wollastonits. Naturwissenschaften 41, 551 (1954) Henmi, Ch., Kawahara, A., Henmi, K., Kusachi, 1., Takeuchi, Y.: The 3T, 4T and 5T polytypes of wollastonite from Kushiro, Hiroshima Prefecture, Japan. Am. Mineral. 68, (1983) Henmi, Ch., Kusachi, 1., Kawahara, A., Henmi, K.: 7T wollastonite from Fuka, Okayama Prefecture. Mineral J. 9, Nr. 3, (1978) Homstra, J., Vossers, H.: Das Philips Einkristalldiffraktometer. Philips Tech. Rundsch. 33, Nr. 3, (1973/74) International tables for X-ray crystallography, Vol. IV. The Kynoch Press, Birmingham (1974) Jeffery, J. W., Heller, L.: Preliminary X-ray investigation of pseudo-wollastonite. Acta Crystallogr. 6, (1953) Mamedov, KH. S., Belov, N. V.: The crystalline structure of wollastonite. Dokl. Acad. Sci. USSR 107, (1956) Ohashi, Y, Finger, L. W.: The role of octahedral cations in pyroxenoid crystal chemistry. 1. Bustamite, wollastonite, and the pectolite-schizolite-serandite series. Am. Mineral. 63, (1978) She1drick, G. M.: SHELX-76. Program for crystal structure determination. Univ. of Cambridge, England (1976) Stout, G. H., Jensen, L. H.: X-ray structure determination. New York: Macmillan (1968), p. 457 Tolliday, J.: Crystal structure of {i-wollastonite. Nature 182, (1958) Trojer, F. J.: The crystal structure of parawollastonite. Z. Kristallogr. 127, (1968) Wenk, H.-R.: Polymorphism of Wollastonite. Contrib. Mineral. Petrol. 22, (1969) Yamanaka, B. T., Mori, H.: The Structure and Polytypes of a-casi03 (Pseudowollastonite). Acta Crystallogr. 37, (1981)