- Email: [email protected]
Crystal structures of the R3Mg0.5GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds
Journal of Alloys and Compounds 424 (2006) 114–118
Crystal structures of the R3Mg0.5GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds M.R. Huch ∗ , L.D. Gulay, I.D. Olekseyuk Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk, Ukraine Received 21 November 2005; received in revised form 7 December 2005; accepted 10 December 2005 Available online 3 February 2006
Abstract The crystal structures of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds (La3 CuSiS7 structure type, space group P63 , Pearson symbol hP23) were determined by means of X-ray powder diffraction: a = 0.9788(1) nm, c = 0.57745(5) nm, RBragg = 0.0814 (Y3 Mg0.5 GeS7 ); a = 1.0262(2) nm, c = 0.57849(7) nm, RBragg = 0.0687 (Ce3 Mg0.5 GeS7 ); a = 1.01249(3) nm, c = 0.58040(2) nm, RBragg = 0.0832 (Pr3 Mg0.5 GeS7 ); a = 1.00701(3) nm, c = 0.58047(3) nm, RBragg = 0.0636 (Nd3 Mg0.5 GeS7 ); a = 0.99500(3) nm, c = 0.57872(3) nm, RBragg = 0.0870 (Sm3 Mg0.5 GeS7 ); a = 0.99319(3) nm, c = 0.57083(3) nm, RBragg = 0.0901 (Gd3 Mg0.5 GeS7 ); a = 0.98007(5) nm, c = 0.57843(4) nm, RBragg = 0.0859 (Tb3 Mg0.5 GeS7 ); a = 0.97698(4) nm, c = 0.57675(5) nm, RBragg = 0.0931 (Dy3 Mg0.5 GeS7 ); a = 0.9735(2) nm, c = 0.57941(7) nm, RBragg = 0.0763 (Ho3 Mg0.5 GeS7 ); a = 0.9694(2) nm, c = 0.57994(7) nm, RBragg = 0.0724 (Er3 Mg0.5 GeS7 ). The R-centered trigonal prisms, Mg-centered octahedra and Ge-centered tetrahedra can be selected in the crystal structure of the R3 Mg0.5 GeS7 compounds. © 2005 Elsevier B.V. All rights reserved. Keywords: Chalcogenides; Rare earth compounds; Mg compounds; Ge compounds; S compounds; Crystal structure; X-ray powder diffraction
1. Introduction The rare earth chalcogenide materials are very interesting over last years due to their thermal, electrical and optical properties. Therefore the synthesis and the investigation of the crystal structures of new complex chalcogenides is important step in a search for new materials. The existence of quaternary R3 Mg0.5 Si(Ge)S7 (R = Y, La) compounds (Ce6 Al10/3 S14 structure type, space group P63 ) has been reported in Ref. [1]. Lattice parameters have been determined. Complete crystal structure determination of quaternary rare-earth sulphides La3 Mg0.5 GeS7 and La3 Mg0.5 SiS7 have been reported in Ref. [2]. Structurally, these phases are members of the large family of the compounds with the general formula R3 MX3 TX4 (space group P63 ), where R—lanthanide element, M—mono-valent element (Cu, Ag) or 1/2 of di-valent element (Mg, Ni, Mn), T—Si, Ge, Sn and X—S, Se. The crystal structures of the compounds Y3 CuSiS7 , Y3 CuSiSe7 [3], La3 CuSiS7 [4], Y3 CuGeS7 [5], Y3 CuGeSe7 [6], La3 CuGeS7 , La3 CuGeSe7
∗
Corresponding author. E-mail address: [email protected] (M.R. Huch).
0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2005.12.025
[7] and Dy3 CuGeSe7 [8] have been determined. The crystal structure of the La3 AgSiSe7 compound has been reported in Ref. [9]. The crystal structures of the compounds R3 CuSnS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Ho) [10,11], R3 CuSnSe7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy) [12,13] have been reported recently. This paper presents part of a systematic investigation of rare earth chalcogenides. The crystal structures of quaternary R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds are given. 2. Experimental details The samples were prepared by fusion of the high purity elements (the purity of the ingredients was better than 99.9 wt.%) in evacuated silica ampoules. In order to exclude the reaction of magnesium with quartz the ampoules were covered by graphite. The synthesis was realized in a tube furnace. The ampoules were heated with the heating rate of 30 K/h to maximal temperature 1420 K. The samples were kept at maximal temperature during 4 h. After that they were cooled slowly (10 K/h) to 870 K and annealed at this temperature during 240 h. After annealing the ampoules with the samples were quenched in cold water. The prepared products were brown-coloured compact samples. X-ray powder diffraction patterns of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds for the crystal structure determination were recorded using a DRON-4-13 powder diffractometer (Cu K␣ radiation,
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
115
Table 1 Results of the crystal structure determination of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds Compound
a (nm)
c (nm)
c/a
V (nm3 )
Calculated density (g/cm3 )
RBragg
RP
Y3 Mg0.5 GeS7 Ce3 Mg0.5 GeS7 Pr3 Mg0.5 GeS7 Nd3 Mg0.5 GeS7 Sm3 Mg0.5 GeS7 Gd3 Mg0.5 GeS7 Td3 Mg0.5 GeS7 Dy3 Mg0.5 GeS7 Ho3 Mg0.5 GeS7 Er3 Mg0.5 GeS7
0.9788(1) 1.0262(2) 1.01249(3) 1.00701(3) 0.99500(3) 0.99319(3) 0.98007(5) 0.97698(4) 0.9735(2) 0.9694(2)
0.57745(5) 0.57849(7) 0.58040(2) 0.58047(3) 0.57872(3) 0.57083(3) 0.57843(4) 0.57675(5) 0.57941(7) 0.57994(7)
0.5900 0.5637 0.5732 0.5764 0.5816 0.5747 0.5902 0.5903 0.5951 0.5982
0.4791(2) 0.5275(3) 0.51528(5) 0.50977(6) 0.49619(6) 0.48765(6) 0.48117(8) 0.4785(3) 0.4755(3) 0.4720(3)
3.992 4.592 4.716 4.832 5.087 5.317 5.424 5.529 5.614 5.706
0.0814 0.0687 0.0832 0.0636 0.0870 0.0901 0.0859 0.0931 0.0763 0.0724
0.0726 0.0732 0.1615 0.1515 0.1519 0.1849 0.1699 0.1863 0.0534 0.0668
Table 2 Atomic coordinates and isotropic temperature factors for the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds Compound
R 6(c) x y z Biso × 102 (nm2 )
Mga 2(a) 0 0 z Biso × 102 (nm2 )
Geb 2(b) 1/3 2/3 z Biso × 102 (nm2 )
S1 2(b) 1/3 2/3 z Biso × 102 (nm2 )
S2 6(c) x y z Biso × 102 (nm2 )
S3 6(c) x y z Biso × 102 (nm2 )
Y3 Mg0.5 GeS7
x = 0.2231(5) y = 0.3588(7) z = 0.762(2) B = 0.5
z = 0.96(2) B = 0.5
B = 0.5
z = 0.964(6) B = 0.5
x = 0.421(2) y = 0.905(2) z = 0.499(4) B = 0.5
x = 0.908(2) y = 0.161(2) z = 0.724(5) B = 0.5
Ce3 Mg0.5 GeS7
x = 0.2323(5) y = 0.3577(6) z = 0.746(3) B = 0.5
z = 0.93(2) B = 0.5
B = 0.5
z = 0.975(7) B = 0.5
x = 0.424(2) y = 0.903(3) z = 0.501(6) B = 0.5
x = 0.911(2) y = 0.153(2) z = 0.756(9) B = 0.5
Pr3 Mg0.5 GeS7
x = 0.2278(2) y = 0.3562(2) z = 0.744(1) B = 0.68(3)
z = 0.95(1) B = 1.6(8)
B = 0.32(5)
z = 0.954(3) B = 0.44(5)
x = 0.421(1) y = 0.904(1) z = 0.491(2) B = 1.2(3)
x = 0.9081(8) y = 0.1621(8) z = 0.723(2) B = 0.4(2)
Nd3 Mg0.5 GeS7
x = 0.2266(2) y = 0.3562(2) z = 0.7523(8) B = 1.02(3)
z = 0.964(8) B = 1.1(7)
B = 0.2(2)
z = 0.951(2) B = 0.37(5)
x = 0.4260(9) y = 0.903(1) z = 0.478(2) B = 1.1(3)
x = 0.9112(8) y = 0.1605(8) z = 0.711(2) B = 1.3(2)
Sm3 Mg0.5 GeS7
x = 0.2252(2) y = 0.3573(2) z = 0.753(1) B = 1.04(6)
z = 0.95(1) B = 1.5(9)
B = 0.3(2)
z = 0.959(3) B = 0.3(3)
x = 0.4226(9) y = 0.903(1) z = 0.491(2) B = 0.3(3)
x = 0.9020(8) y = 0.1572(8) z = 0.726(2) B = 1.4(3)
Gd3 Mg0.5 GeS7
x = 0.2286(2) y = 0.3590(3) z = 0.749(1) B = 0.5
z = 0.97(1) B = 0.5
B = 0.5
z = 0.970(3) B = 0.5
x = 0.415(1) y = 0.893(1) z = 0.497(2) B = 0.5
x = 0.906(1) y = 0.158(1) z = 0.730(3) B = 0.5
Tb3 Mg0.5 GeS7
x = 0.2238(1) y = 0.3573(2) z = 0.7637(8) B = 0.5
z = 0.989(9) B = 0.5
B = 0.5
z = 0.958(2) B = 0.5
x = 0.4299(8) y = 0.9067(8) z = 0.510(1) B = 0.5
x = 0.8999(7) y = 0.1652(7) z = 0.715(1) B = 0.5
Dy3 Mg0.5 GeS7
x = 0.2231(2) y = 0.3594(3) z = 0.759(1) B = 0.5
z = 0.98(1) B = 0.5
B = 0.5
z = 0.952(3) B = 0.5
x = 0.421(1) y = 0.909(1) z = 0.499(2) B = 0.5
x = 0.899(1) y = 0.154(1) z = 0.716(2) B = 0.5
Ho3 Mg0.5 GeS7
x = 0.2200(5) y = 0.3599(7) z = 0.758(3) B = 0.5
z = 0.95(3) B = 0.5
B = 0.5
z = 0.980(8) B = 0.5
x = 0.422(3) y = 0.910(3) z = 0.507(6) B = 0.5
x = 0.898(3) y = 0.150(3) z = 0.706(6) B = 0.5
Er3 Mg0.5 GeS7
x = 0.2201(7) y = 0.3605(7) z = 0.755(4) B = 0.5
z = 0.95(3) B = 0.5
B = 0.5
z = 0.972(8) B = 0.5
x = 0.431(4) y = 0.904(3) z = 0.507(8) B = 0.5
x = 0.901(3) y = 0.156(3) z = 0.703(7) B = 0.5
a b
Mg = 0.50 Mg. Fixed (z = 0.333).
116
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
Fig. 1. The experimental and calculated diffractograms and the corresponding difference diagram for Pr3 Mg0.5 GeS7 . 10◦ ≤ 2Θ ≤ 100◦ , step scan mode with a step size of 0.05◦ and counting time of 20 s per data point). Crystal structure determinations were performed using the Rietveld method implemented in the CSD [14] and DBWS-9411 [15] programs.
3. Results and discussion The formation of quaternary R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds was established. The X-ray powder diffraction patterns of these compounds were similar. Single-phase samples of the R3 Mg0.5 GeS7 (R = Pr, Nd, Sm, Gd, Tb, Dy) compounds were obtained. The CSD program was used for the crystal structure determination of these compounds. Since the presence of the minority phases Y2 S3 (Ho2 S3 structure type, space group P21 /m, a = 1.75233 nm, b = 0.40107 nm, c = 1.01736 nm, β = 98.601◦ ) [16], Ce2 S3 (La2 S3 structure type, space group Pnma, a = 0.75323 nm, b = 0.40967 nm, c = 1.57276 nm) [17]), Ho2 S3 (Ho2 S3 structure type, space group P21 /m, a = 1.750 nm, b = 0.4002 nm,
Fig. 2. The dependence of the lattice constants (a, c) and unit cell volumes (V) of the R3 Mg0.5 GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds from the ionic radii of the rare earth elements.
c = 1.015 nm, β = 99.4◦ ) [18] and Er2 S3 (Ho2 S3 structure type, space group P21 /m, a = 1.74418 nm, b = 0.39822 nm, c = 1.01013 nm, β = 98.688◦ ) [19] were observed in the X-ray powder diffraction patterns of the R3 Mg0.5 GeS7 (R = Y, Ce, Ho, Er) compounds, respectively, the DBWS-9411 program was used in the refinement procedure of these compounds. The presence of these minority phases was taken into account during the refinement. The peaks of the X-ray powder diffraction patterns
Fig. 3. The projection of the unit cell and the coordination polyhedra of the Pr (a), Mg (b) Ge (c), S1 (d), S2 (e), S3 (f) atoms in the crystal structure of the Pr3 Mg0.5 GeS7 compound.
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
117
Fig. 4. The packing of Pr-centered trigonal prisms with one additional atom, Mg-centered octahedra and Ge-centered tetrahedra in the structure of the Pr3 Mg0.5 GeS7 compound.
of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds were indexed on the basis of hexagonal unit cell with the lattice parameters listed in Table 1. The crystal structure of the La3 Mg0.5 GeS7 compound (space group P63 ) [2] was used as a starting model for the crystal structure determination of these compounds. Results of the crystal structure determination of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds are given in Table 1. Atomic coordinates and isotropic temperature factors are listed in Table 2. The positions of the Mg atoms are partially occupied (0.50). The positions Table 3 Interatomic distances δ (nm) and coordination numbers (C.N.) of the atoms in the Pr3 Mg0.5 GeS7 structure δ (nm)
C.N.
0.2821(8) 0.2827(9) 0.284(1) 0.292(1) 0.295(1) 0.301(1) 0.3025(7)
7
Mg 3S2 3S2
0.261(4) 0.275(4)
6
Ge 1S1 3S3
0.219 0.230
4
S1 1Ge 3Pr
0.219 0.3025(7)
4
S2 1Mg 1Mg 1Pr 1Pr 1Pr
0.261(4) 0.275(4) 0.2821(8) 0.2827(9) 0.292(1)
5
S3 1Ge 1Pr 1Pr 1Pr
0.230 0.284(1) 0.295(1) 0.301(1)
4
Atoms Pr 1S2 1S2 1S3 1S2 1S3 1S3 1S1
of the remaining atoms are fully occupied. The experimental and calculated diffractograms and the corresponding difference diagram for Pr3 Mg0.5 GeS7 are shown in Fig. 1. The dependence of the lattice constants (a, c) and unit cell volumes (V) of the R3 Mg0.5 GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds from the ionic radii of the rare earth elements [20] are shown in Fig. 2. The unit cell volumes agree well with the ionic radii of the rare earth elements. The lattice constants a correlate well with the sizes of the rare earth ions also. The differences between c constants of the R3 Mg0.5 GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds are not significant comparing with the difference between a constants. The dependence of the lattice constants c from the sizes of the rare earth ions is not regular. The interatomic distances and coordination numbers of the atoms in the structure of the Pr3 Mg0.5 GeS7 compound are given in Table 3. The interatomic distances agree well with the sum of the ionic radii. The projection of the unit cell and the coordination polyhedral of the Pr (a), Mg (b) Ge (c), S1 (d), S2 (e), S3 (f) atoms in the structure of the Pr3 Mg0.5 GeS7 compound are shown in Fig. 3. The Pr atoms are surrounding by seven sulphur atoms which form trigonal prisms with one additional atom. The Mg atoms are located practically in the centres of octahedra, the Ge atoms are located in tetrahedra, The S1 and S3 atoms are located in tetrahedra also. The S2 atoms are surrounded by five cations. The packing of Pr-centered trigonal prisms with one additional atom, Mg-centered octahedra and Ge-centered tetrahedra in the structure of the Pr3 Mg0.5 GeS7 compound are shown in Fig. 4.
References [1] A. Michelet, J. Flahaut, C.H. Hebd, Seances Acad. Sci. 269C (1969) 1203. [2] R.L. Gitzendanner, C.M. Spencer, F.J. DiSalvo, M.A. Pell, J.A. Ibers, J. Solid State Chem. 131 (1996) 399. [3] L.D. Gulay, O.S. Lychmanyuk, J. St˛epie´n-Damm, A. Pietraszko, I.D. Olekseyuk, J. Alloys Compd. 402 (2005) 201. [4] G. Collin, P. Laruelle, Bull. Soc. Fr. Miner. Cristallogr. 94 (1971) 175. [5] L.D. Gulay, O.S. Lychmanyuk, J. St˛epie´n-Damm, A. Pietraszko, I.D. Olekseyuk, J. Alloys Compd., in press. [6] O.S. Lychmanyuk, L.D. Gulay, I.D. Olekseyuk, Pol. J. Chem., in press. [7] K.M. Poduska, F.J. DiSalvo, K. Min, P.S. Halasyamani, J. Alloys Compd. 335 (2002) L5. [8] F.Q. Huang, I.A. Ibers, Acta Crystallogr. C55 (1999) 1210.
118
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
[9] S.-H. Lin, J.-G. Mao, G.-C. Guo, J.-S. Huang, J. Alloys Compd. 252 (1997) L8. [10] L.D. Gulay, V.Ya. Shemet, I.D. Olekseyuk, J. Alloys Compd. 388 (2005) 59. [11] L.D. Gulay, I.D. Olekseyuk, M. Wołcyrz, J. St˛epie´n-Damm, Z. Anorg. Allg. Chem. 631 (2005) 1919. [12] L.D. Gulay, V.Ya. Shemet, I.D. Olekseyuk, J. Alloys Compd. 385 (2004) 160. [13] L.D. Gulay, I.D. Olekseyuk, J. Alloys Compd. 388 (2005) 274. [14] L.G. Aksel’rud, Yu.N. Grin’, P.Yu. Zavalij, V.K. Pecharsky, V.S. Fundamensky, Collected Abstracts from 12th European Crystallographic
[15]
[16] [17] [18] [19] [20]
Meeting, vol. 3, Izv. Acad. Nauk SSSR, Moscow, August 1989. p. 155. R.A. Young, A. Sakthivel, T.S. Moss, C.O. Paria-Santos, Program DBWS9411 for Rietveld Analysis of X-ray and Neutron Powder Diffraction Patterns, Georgia Institute of Technology, Atlanta, GA, 1995. Th. Schleid, European J. Solid State Inorg.Chem. 29 (1992) 1015. Th. Schleid, P. Lauxmann, Z. Anorg. Allg. Chem. 625 (1999) 1053. J.G. White, P.N. Yocom, S. Lerner, Inorg. Chem. 6 (1967) 1872. Th. Schleid, F. Lissner, Z. Anorg. Allg. Chem. 615 (1992) 19. N. Wiberg, Lehrbuch der Anorganischen Chemie, Walter de Gruyter, Berlin, 1995, p. 1838.
Crystal structures of the R3Mg0.5GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds M.R. Huch ∗ , L.D. Gulay, I.D. Olekseyuk Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk, Ukraine Received 21 November 2005; received in revised form 7 December 2005; accepted 10 December 2005 Available online 3 February 2006
Abstract The crystal structures of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds (La3 CuSiS7 structure type, space group P63 , Pearson symbol hP23) were determined by means of X-ray powder diffraction: a = 0.9788(1) nm, c = 0.57745(5) nm, RBragg = 0.0814 (Y3 Mg0.5 GeS7 ); a = 1.0262(2) nm, c = 0.57849(7) nm, RBragg = 0.0687 (Ce3 Mg0.5 GeS7 ); a = 1.01249(3) nm, c = 0.58040(2) nm, RBragg = 0.0832 (Pr3 Mg0.5 GeS7 ); a = 1.00701(3) nm, c = 0.58047(3) nm, RBragg = 0.0636 (Nd3 Mg0.5 GeS7 ); a = 0.99500(3) nm, c = 0.57872(3) nm, RBragg = 0.0870 (Sm3 Mg0.5 GeS7 ); a = 0.99319(3) nm, c = 0.57083(3) nm, RBragg = 0.0901 (Gd3 Mg0.5 GeS7 ); a = 0.98007(5) nm, c = 0.57843(4) nm, RBragg = 0.0859 (Tb3 Mg0.5 GeS7 ); a = 0.97698(4) nm, c = 0.57675(5) nm, RBragg = 0.0931 (Dy3 Mg0.5 GeS7 ); a = 0.9735(2) nm, c = 0.57941(7) nm, RBragg = 0.0763 (Ho3 Mg0.5 GeS7 ); a = 0.9694(2) nm, c = 0.57994(7) nm, RBragg = 0.0724 (Er3 Mg0.5 GeS7 ). The R-centered trigonal prisms, Mg-centered octahedra and Ge-centered tetrahedra can be selected in the crystal structure of the R3 Mg0.5 GeS7 compounds. © 2005 Elsevier B.V. All rights reserved. Keywords: Chalcogenides; Rare earth compounds; Mg compounds; Ge compounds; S compounds; Crystal structure; X-ray powder diffraction
1. Introduction The rare earth chalcogenide materials are very interesting over last years due to their thermal, electrical and optical properties. Therefore the synthesis and the investigation of the crystal structures of new complex chalcogenides is important step in a search for new materials. The existence of quaternary R3 Mg0.5 Si(Ge)S7 (R = Y, La) compounds (Ce6 Al10/3 S14 structure type, space group P63 ) has been reported in Ref. [1]. Lattice parameters have been determined. Complete crystal structure determination of quaternary rare-earth sulphides La3 Mg0.5 GeS7 and La3 Mg0.5 SiS7 have been reported in Ref. [2]. Structurally, these phases are members of the large family of the compounds with the general formula R3 MX3 TX4 (space group P63 ), where R—lanthanide element, M—mono-valent element (Cu, Ag) or 1/2 of di-valent element (Mg, Ni, Mn), T—Si, Ge, Sn and X—S, Se. The crystal structures of the compounds Y3 CuSiS7 , Y3 CuSiSe7 [3], La3 CuSiS7 [4], Y3 CuGeS7 [5], Y3 CuGeSe7 [6], La3 CuGeS7 , La3 CuGeSe7
∗
Corresponding author. E-mail address: [email protected] (M.R. Huch).
0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2005.12.025
[7] and Dy3 CuGeSe7 [8] have been determined. The crystal structure of the La3 AgSiSe7 compound has been reported in Ref. [9]. The crystal structures of the compounds R3 CuSnS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Ho) [10,11], R3 CuSnSe7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy) [12,13] have been reported recently. This paper presents part of a systematic investigation of rare earth chalcogenides. The crystal structures of quaternary R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds are given. 2. Experimental details The samples were prepared by fusion of the high purity elements (the purity of the ingredients was better than 99.9 wt.%) in evacuated silica ampoules. In order to exclude the reaction of magnesium with quartz the ampoules were covered by graphite. The synthesis was realized in a tube furnace. The ampoules were heated with the heating rate of 30 K/h to maximal temperature 1420 K. The samples were kept at maximal temperature during 4 h. After that they were cooled slowly (10 K/h) to 870 K and annealed at this temperature during 240 h. After annealing the ampoules with the samples were quenched in cold water. The prepared products were brown-coloured compact samples. X-ray powder diffraction patterns of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds for the crystal structure determination were recorded using a DRON-4-13 powder diffractometer (Cu K␣ radiation,
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
115
Table 1 Results of the crystal structure determination of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds Compound
a (nm)
c (nm)
c/a
V (nm3 )
Calculated density (g/cm3 )
RBragg
RP
Y3 Mg0.5 GeS7 Ce3 Mg0.5 GeS7 Pr3 Mg0.5 GeS7 Nd3 Mg0.5 GeS7 Sm3 Mg0.5 GeS7 Gd3 Mg0.5 GeS7 Td3 Mg0.5 GeS7 Dy3 Mg0.5 GeS7 Ho3 Mg0.5 GeS7 Er3 Mg0.5 GeS7
0.9788(1) 1.0262(2) 1.01249(3) 1.00701(3) 0.99500(3) 0.99319(3) 0.98007(5) 0.97698(4) 0.9735(2) 0.9694(2)
0.57745(5) 0.57849(7) 0.58040(2) 0.58047(3) 0.57872(3) 0.57083(3) 0.57843(4) 0.57675(5) 0.57941(7) 0.57994(7)
0.5900 0.5637 0.5732 0.5764 0.5816 0.5747 0.5902 0.5903 0.5951 0.5982
0.4791(2) 0.5275(3) 0.51528(5) 0.50977(6) 0.49619(6) 0.48765(6) 0.48117(8) 0.4785(3) 0.4755(3) 0.4720(3)
3.992 4.592 4.716 4.832 5.087 5.317 5.424 5.529 5.614 5.706
0.0814 0.0687 0.0832 0.0636 0.0870 0.0901 0.0859 0.0931 0.0763 0.0724
0.0726 0.0732 0.1615 0.1515 0.1519 0.1849 0.1699 0.1863 0.0534 0.0668
Table 2 Atomic coordinates and isotropic temperature factors for the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds Compound
R 6(c) x y z Biso × 102 (nm2 )
Mga 2(a) 0 0 z Biso × 102 (nm2 )
Geb 2(b) 1/3 2/3 z Biso × 102 (nm2 )
S1 2(b) 1/3 2/3 z Biso × 102 (nm2 )
S2 6(c) x y z Biso × 102 (nm2 )
S3 6(c) x y z Biso × 102 (nm2 )
Y3 Mg0.5 GeS7
x = 0.2231(5) y = 0.3588(7) z = 0.762(2) B = 0.5
z = 0.96(2) B = 0.5
B = 0.5
z = 0.964(6) B = 0.5
x = 0.421(2) y = 0.905(2) z = 0.499(4) B = 0.5
x = 0.908(2) y = 0.161(2) z = 0.724(5) B = 0.5
Ce3 Mg0.5 GeS7
x = 0.2323(5) y = 0.3577(6) z = 0.746(3) B = 0.5
z = 0.93(2) B = 0.5
B = 0.5
z = 0.975(7) B = 0.5
x = 0.424(2) y = 0.903(3) z = 0.501(6) B = 0.5
x = 0.911(2) y = 0.153(2) z = 0.756(9) B = 0.5
Pr3 Mg0.5 GeS7
x = 0.2278(2) y = 0.3562(2) z = 0.744(1) B = 0.68(3)
z = 0.95(1) B = 1.6(8)
B = 0.32(5)
z = 0.954(3) B = 0.44(5)
x = 0.421(1) y = 0.904(1) z = 0.491(2) B = 1.2(3)
x = 0.9081(8) y = 0.1621(8) z = 0.723(2) B = 0.4(2)
Nd3 Mg0.5 GeS7
x = 0.2266(2) y = 0.3562(2) z = 0.7523(8) B = 1.02(3)
z = 0.964(8) B = 1.1(7)
B = 0.2(2)
z = 0.951(2) B = 0.37(5)
x = 0.4260(9) y = 0.903(1) z = 0.478(2) B = 1.1(3)
x = 0.9112(8) y = 0.1605(8) z = 0.711(2) B = 1.3(2)
Sm3 Mg0.5 GeS7
x = 0.2252(2) y = 0.3573(2) z = 0.753(1) B = 1.04(6)
z = 0.95(1) B = 1.5(9)
B = 0.3(2)
z = 0.959(3) B = 0.3(3)
x = 0.4226(9) y = 0.903(1) z = 0.491(2) B = 0.3(3)
x = 0.9020(8) y = 0.1572(8) z = 0.726(2) B = 1.4(3)
Gd3 Mg0.5 GeS7
x = 0.2286(2) y = 0.3590(3) z = 0.749(1) B = 0.5
z = 0.97(1) B = 0.5
B = 0.5
z = 0.970(3) B = 0.5
x = 0.415(1) y = 0.893(1) z = 0.497(2) B = 0.5
x = 0.906(1) y = 0.158(1) z = 0.730(3) B = 0.5
Tb3 Mg0.5 GeS7
x = 0.2238(1) y = 0.3573(2) z = 0.7637(8) B = 0.5
z = 0.989(9) B = 0.5
B = 0.5
z = 0.958(2) B = 0.5
x = 0.4299(8) y = 0.9067(8) z = 0.510(1) B = 0.5
x = 0.8999(7) y = 0.1652(7) z = 0.715(1) B = 0.5
Dy3 Mg0.5 GeS7
x = 0.2231(2) y = 0.3594(3) z = 0.759(1) B = 0.5
z = 0.98(1) B = 0.5
B = 0.5
z = 0.952(3) B = 0.5
x = 0.421(1) y = 0.909(1) z = 0.499(2) B = 0.5
x = 0.899(1) y = 0.154(1) z = 0.716(2) B = 0.5
Ho3 Mg0.5 GeS7
x = 0.2200(5) y = 0.3599(7) z = 0.758(3) B = 0.5
z = 0.95(3) B = 0.5
B = 0.5
z = 0.980(8) B = 0.5
x = 0.422(3) y = 0.910(3) z = 0.507(6) B = 0.5
x = 0.898(3) y = 0.150(3) z = 0.706(6) B = 0.5
Er3 Mg0.5 GeS7
x = 0.2201(7) y = 0.3605(7) z = 0.755(4) B = 0.5
z = 0.95(3) B = 0.5
B = 0.5
z = 0.972(8) B = 0.5
x = 0.431(4) y = 0.904(3) z = 0.507(8) B = 0.5
x = 0.901(3) y = 0.156(3) z = 0.703(7) B = 0.5
a b
Mg = 0.50 Mg. Fixed (z = 0.333).
116
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
Fig. 1. The experimental and calculated diffractograms and the corresponding difference diagram for Pr3 Mg0.5 GeS7 . 10◦ ≤ 2Θ ≤ 100◦ , step scan mode with a step size of 0.05◦ and counting time of 20 s per data point). Crystal structure determinations were performed using the Rietveld method implemented in the CSD [14] and DBWS-9411 [15] programs.
3. Results and discussion The formation of quaternary R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds was established. The X-ray powder diffraction patterns of these compounds were similar. Single-phase samples of the R3 Mg0.5 GeS7 (R = Pr, Nd, Sm, Gd, Tb, Dy) compounds were obtained. The CSD program was used for the crystal structure determination of these compounds. Since the presence of the minority phases Y2 S3 (Ho2 S3 structure type, space group P21 /m, a = 1.75233 nm, b = 0.40107 nm, c = 1.01736 nm, β = 98.601◦ ) [16], Ce2 S3 (La2 S3 structure type, space group Pnma, a = 0.75323 nm, b = 0.40967 nm, c = 1.57276 nm) [17]), Ho2 S3 (Ho2 S3 structure type, space group P21 /m, a = 1.750 nm, b = 0.4002 nm,
Fig. 2. The dependence of the lattice constants (a, c) and unit cell volumes (V) of the R3 Mg0.5 GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds from the ionic radii of the rare earth elements.
c = 1.015 nm, β = 99.4◦ ) [18] and Er2 S3 (Ho2 S3 structure type, space group P21 /m, a = 1.74418 nm, b = 0.39822 nm, c = 1.01013 nm, β = 98.688◦ ) [19] were observed in the X-ray powder diffraction patterns of the R3 Mg0.5 GeS7 (R = Y, Ce, Ho, Er) compounds, respectively, the DBWS-9411 program was used in the refinement procedure of these compounds. The presence of these minority phases was taken into account during the refinement. The peaks of the X-ray powder diffraction patterns
Fig. 3. The projection of the unit cell and the coordination polyhedra of the Pr (a), Mg (b) Ge (c), S1 (d), S2 (e), S3 (f) atoms in the crystal structure of the Pr3 Mg0.5 GeS7 compound.
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
117
Fig. 4. The packing of Pr-centered trigonal prisms with one additional atom, Mg-centered octahedra and Ge-centered tetrahedra in the structure of the Pr3 Mg0.5 GeS7 compound.
of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds were indexed on the basis of hexagonal unit cell with the lattice parameters listed in Table 1. The crystal structure of the La3 Mg0.5 GeS7 compound (space group P63 ) [2] was used as a starting model for the crystal structure determination of these compounds. Results of the crystal structure determination of the R3 Mg0.5 GeS7 (R = Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds are given in Table 1. Atomic coordinates and isotropic temperature factors are listed in Table 2. The positions of the Mg atoms are partially occupied (0.50). The positions Table 3 Interatomic distances δ (nm) and coordination numbers (C.N.) of the atoms in the Pr3 Mg0.5 GeS7 structure δ (nm)
C.N.
0.2821(8) 0.2827(9) 0.284(1) 0.292(1) 0.295(1) 0.301(1) 0.3025(7)
7
Mg 3S2 3S2
0.261(4) 0.275(4)
6
Ge 1S1 3S3
0.219 0.230
4
S1 1Ge 3Pr
0.219 0.3025(7)
4
S2 1Mg 1Mg 1Pr 1Pr 1Pr
0.261(4) 0.275(4) 0.2821(8) 0.2827(9) 0.292(1)
5
S3 1Ge 1Pr 1Pr 1Pr
0.230 0.284(1) 0.295(1) 0.301(1)
4
Atoms Pr 1S2 1S2 1S3 1S2 1S3 1S3 1S1
of the remaining atoms are fully occupied. The experimental and calculated diffractograms and the corresponding difference diagram for Pr3 Mg0.5 GeS7 are shown in Fig. 1. The dependence of the lattice constants (a, c) and unit cell volumes (V) of the R3 Mg0.5 GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds from the ionic radii of the rare earth elements [20] are shown in Fig. 2. The unit cell volumes agree well with the ionic radii of the rare earth elements. The lattice constants a correlate well with the sizes of the rare earth ions also. The differences between c constants of the R3 Mg0.5 GeS7 (R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) compounds are not significant comparing with the difference between a constants. The dependence of the lattice constants c from the sizes of the rare earth ions is not regular. The interatomic distances and coordination numbers of the atoms in the structure of the Pr3 Mg0.5 GeS7 compound are given in Table 3. The interatomic distances agree well with the sum of the ionic radii. The projection of the unit cell and the coordination polyhedral of the Pr (a), Mg (b) Ge (c), S1 (d), S2 (e), S3 (f) atoms in the structure of the Pr3 Mg0.5 GeS7 compound are shown in Fig. 3. The Pr atoms are surrounding by seven sulphur atoms which form trigonal prisms with one additional atom. The Mg atoms are located practically in the centres of octahedra, the Ge atoms are located in tetrahedra, The S1 and S3 atoms are located in tetrahedra also. The S2 atoms are surrounded by five cations. The packing of Pr-centered trigonal prisms with one additional atom, Mg-centered octahedra and Ge-centered tetrahedra in the structure of the Pr3 Mg0.5 GeS7 compound are shown in Fig. 4.
References [1] A. Michelet, J. Flahaut, C.H. Hebd, Seances Acad. Sci. 269C (1969) 1203. [2] R.L. Gitzendanner, C.M. Spencer, F.J. DiSalvo, M.A. Pell, J.A. Ibers, J. Solid State Chem. 131 (1996) 399. [3] L.D. Gulay, O.S. Lychmanyuk, J. St˛epie´n-Damm, A. Pietraszko, I.D. Olekseyuk, J. Alloys Compd. 402 (2005) 201. [4] G. Collin, P. Laruelle, Bull. Soc. Fr. Miner. Cristallogr. 94 (1971) 175. [5] L.D. Gulay, O.S. Lychmanyuk, J. St˛epie´n-Damm, A. Pietraszko, I.D. Olekseyuk, J. Alloys Compd., in press. [6] O.S. Lychmanyuk, L.D. Gulay, I.D. Olekseyuk, Pol. J. Chem., in press. [7] K.M. Poduska, F.J. DiSalvo, K. Min, P.S. Halasyamani, J. Alloys Compd. 335 (2002) L5. [8] F.Q. Huang, I.A. Ibers, Acta Crystallogr. C55 (1999) 1210.
118
M.R. Huch et al. / Journal of Alloys and Compounds 424 (2006) 114–118
[9] S.-H. Lin, J.-G. Mao, G.-C. Guo, J.-S. Huang, J. Alloys Compd. 252 (1997) L8. [10] L.D. Gulay, V.Ya. Shemet, I.D. Olekseyuk, J. Alloys Compd. 388 (2005) 59. [11] L.D. Gulay, I.D. Olekseyuk, M. Wołcyrz, J. St˛epie´n-Damm, Z. Anorg. Allg. Chem. 631 (2005) 1919. [12] L.D. Gulay, V.Ya. Shemet, I.D. Olekseyuk, J. Alloys Compd. 385 (2004) 160. [13] L.D. Gulay, I.D. Olekseyuk, J. Alloys Compd. 388 (2005) 274. [14] L.G. Aksel’rud, Yu.N. Grin’, P.Yu. Zavalij, V.K. Pecharsky, V.S. Fundamensky, Collected Abstracts from 12th European Crystallographic
[15]
[16] [17] [18] [19] [20]
Meeting, vol. 3, Izv. Acad. Nauk SSSR, Moscow, August 1989. p. 155. R.A. Young, A. Sakthivel, T.S. Moss, C.O. Paria-Santos, Program DBWS9411 for Rietveld Analysis of X-ray and Neutron Powder Diffraction Patterns, Georgia Institute of Technology, Atlanta, GA, 1995. Th. Schleid, European J. Solid State Inorg.Chem. 29 (1992) 1015. Th. Schleid, P. Lauxmann, Z. Anorg. Allg. Chem. 625 (1999) 1053. J.G. White, P.N. Yocom, S. Lerner, Inorg. Chem. 6 (1967) 1872. Th. Schleid, F. Lissner, Z. Anorg. Allg. Chem. 615 (1992) 19. N. Wiberg, Lehrbuch der Anorganischen Chemie, Walter de Gruyter, Berlin, 1995, p. 1838.