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Crystal structures of the R3.33CuPb1.5Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds
Journal of Alloys and Compounds 396 (2005) 233–239
Crystal structures of the R3.33CuPb1.5Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds L.D. Gulay ∗ , I.D. Olekseyuk Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk, Ukraine Received 18 December 2004; accepted 4 January 2005 Available online 10 February 2005
Abstract The crystal structures of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds (space group Cm, Pearson symbol mC25.67) were determined by means of X-ray powder diffraction: a = 1.3624(3) nm, b = 0.41144(8) nm, c = 1.2645(3) nm, β = 104.68(1)◦ (for Tb3.33 CuPb1.5 Se7 ); a = 1.3557(5) nm, b = 0.4091(1) nm, c = 1.2574(4) nm, β = 104.59(2)◦ (for Dy3.33 CuPb1.5 Se7 ); a = 1.35314(8) nm, b = 0.40819(2) nm, c = 1.25609(7) nm, β = 104.577(3)◦ , RI = 0.0797 (for Ho3.33 CuPb1.5 Se7 ); a = 1.35018(7) nm, b = 0.40693(2) nm, c = 1.25433(6) nm, β = 104.492(2)◦ , RI = 0.0845 (for Er3.33 CuPb1.5 Se7 ); a = 1.34584(7) nm, b = 0.40560(2) nm, c = 1.25083(6) nm, β = 104.342(3)◦ , RI = 0.0866 (for Tm3.33 CuPb1.5 Se7 ); a = 1.3425(2) nm, b = 0.40437(4) nm, c = 1.2484(1) nm, β = 104.381(8)◦ (for Yb3.33 CuPb1.5 Se7 ) and single crystal diffraction: a = 1.3404(2) nm, b = 0.40307(6) nm, c = 1.2475(2) nm, β = 104.36(1)◦ , R1 = 0.0438 (for Lu3.33 CuPb1.5 Se7 ). The crystal structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds can be derived from the structure of the binary Y5 Se7 compound. The positions of the Y (R) atoms with octahedral coordination in the binary Y5 Se7 compound and the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds are similar. Every position of the Y atom with trigonal prismatic coordination in the Y5 Se7 compound corresponds to two defect positions of the atoms of the statistical mixture M (R + Pb) or Pb in the structures of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds. Additional position of the Cu atoms with tetrahedral coordination exists in the structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds when compared with Y5 Se7 . © 2005 Elsevier B.V. All rights reserved. Keywords: Chalcogenides; Rare earth compounds; Cu compounds; Pb compounds; Se compounds; Crystal structure; X-ray single crystal diffraction; X-ray powder diffraction
1. Introduction The existence of the compounds with the compositions RCuSe2 R2/3 Cu2 Se2 (R = Sc, Y, Tb, Dy, Ho, Er, Tm, Yb and Lu) and GdCu3 Se3 (ErCu3 S3 structure type, space group ¯ has been reported in Refs. [1,2]. According to Ref. [2] P 3) the RCuSe2 (R = La, Ce, Pr, Nd, Sm and Gd) compounds adopt the LaCuS2 structure type (space group P21 /c). The R2 Se3 R5 CuSe8 (R = La, Ce, Pr, Nd, Sm and Gd) solid so¯ have been lutions (Th3 P4 structure type, space group I43d) ∗
Corresponding author. E-mail address: [email protected] (L.D. Gulay).
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established in Refs. [2,3]. The orthorhombic unit cell has been found for the compound with the composition La5 Cu13 Se14 [2]. The existence of the R2 Se3 R2 PbSe4 (R = La, Ce, Pr, Nd and Sm) solid solutions with Th3 P4 structure type (space ¯ group I43d) and the R2 PbSe4 (R = Er, Tm, Yb and Lu) compounds with CaFe2 O4 structure type (space group Pnma) has been reported in Ref. [4]. The Gd(Tb)2 Se3 based solid ¯ in the solutions (Th3 P4 structure type, space group I43d) Gd(Tb)2 Se3 PbSe systems has been also established in Ref. [4]. The existence of the Y3 Cu0.685 Se6 [5], Sm3 CuSe6 [6], R3 CuSe6 (R = Gd, Tb and Dy) [7] compounds (Sm3 CuSe6 structure type, space group Pbcm) has been established recently. The crystal structures of the RCuPbSe3 (R = Y, Gd, Tb,
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Dy, Ho, Er, Tm, Yb and Lu) (-BaLaCuSe3 structure type, space group Pnma) have been determined in Refs. [5,8]. The crystal structures of new quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds are given in the present paper.
Table 1 Crystal data and structure refinement details of the Lu3.33 CuPb1.5 Se7 compound
2. Experimental details
Volume Number of formula units per unit cell Calculated density Absorption coefficient F(0 0 0) Crystal size Θ range for data collection Index ranges
The samples were prepared by melting the high purity starting elements (the purity of the ingredients was better than 99.9 wt.%) in evacuated quartz ampoules. The synthesis was realized in a shaft furnace. The ampoules were heated with a heating rate of 30 K/h to the maximal temperature, 1420 K. The samples were kept at the 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. A single crystal of the Lu3.33 CuPb1.5 Se7 compound was selected from the sample of the corresponding composition for a crystal structure determination. The X-ray intensity data were collected on a KUMA diffraction KM-4 fourcircle single crystal diffractometer equipped with a CCD camera using graphite-monochromatized Mo K␣ radiation (λ = 0.071073 nm). The intensities of the reflections were corrected for Lorentz and polarisation factors. A semiempirical absorption correction was applied. The crystal structure was solved by Patterson methods [9] and refined by a full matrix least squares method using the SHELX-97 program [10]. X-ray powder diffraction patterns of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm and Yb) compounds for the crystal structure determination were recorded using a DRON4-13 (Cu K␣ radiation, 10◦ ≤ 2Θ ≤ 100◦ , step scan mode with a step size of 0.05◦ and counting time of 20 s per data point). Crystal structure determination was performed using the DBWS-9411 [11] program.
3. Results and discussion The formation of new quaternary R3.33 CuPb1.5 Se7 compounds was observed during the investigation of the phase relations in the R2 Se3 Cu2 Se PbSe (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) systems. The similarity of the X-ray powder diffraction patterns of these compounds allows us to conclude that they are isostructural. A good quality single crystal of the Lu3.33 CuPb1.5 Se7 compound was selected from the sample of the corresponding composition. The extinctions were found to be consistent with the centrosymmetric space group C2/m and the non-centrosymmetric space group Cm. Refinements were performed within both space groups. Similar structural models were obtained. Some difference was observed for the positions of the Cu atoms. A better structural model was obtained in case of the noncentrosymmetric space group Cm. The crystal data and the
Empirical formula Formula weight Space group Unit cell dimensions
Reflections collected Independent reflections Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I > 2σ(I)] R indices (all data) Extinction coefficient Largest diffraction peak and hole ×10−3
Lu3.33 CuPb1.5 Se7 1510.56 Cm (No. 8) a = 1.3404(2) nm, b = 0.40307(6) nm, c = 1.2475(2) nm, β = 104.36(1)◦ 0.6529(2) nm3 2 7.683 g/cm3 65.297 mm−1 1254 0.07 mm × 0.08 mm × 0.15 mm 3.15–27.10 −17 ≤ h ≤ 18, −5 ≤ k ≤ 5, −17 ≤ l ≤ 16 3973 1780 [R(int.) = 0.0802] Full-matrix least-square on F2 1780/0/90 1.011 R1 = 0.0438, wR2 = 0.0775 R1 = 0.0803, wR2 = 0.0879 0.00155(7) 3.121 and −3.080 electrons/nm3
refinement information are summarized in Table 1. The final atomic coordinates and temperature factors are given in Table 2. At the first stage, one position of the atoms of the statistical mixture M (0.33Lu + 0.50Pb) and one position of the Pb atoms with occupation factor 1.00 were determined for the Lu3.33 CuPb1.5 Se7 compound similar to the structure of the Y3.33 CuPb1.5 Se7 compound reported in our recent paper [12]. Unusual values of the anisotropic thermal parameters for the atoms of the statistical mixture M (0.33Lu + 0.50Pb), the Pb atoms and a residual electron density of about 11 electrons/10−3 nm3 near those atoms were observed at this stage. At the second stage the positions of the atoms of the statistical mixture M (0.33Lu + 0.50Pb) were split into two close positions M1 (0.17Lu + 0.25Pb) and M2 (0.17Lu + 0.25Pb). The Pb atoms were also located in two close positions with occupation factors 0.50. At this stage the anisotropic thermal parameters for the atoms of the statistical mixtures M1, M2 and the Pb1, Pb2 atoms were significantly reduced. The final value of R1 factor was improved significantly from 0.0685 to 0.0438. The crystal structures of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm and Yb) compounds were investigated using X-ray powder diffraction. X-ray powder diffraction patterns of the R3.33 CuPb1.5 Se7 (R = Tb, Dy and Yb) samples were not of good quality for a reliable crystal structure investigation. Only lattice parameters were determined for those compounds: a = 1.3624(3) nm, b = 0.41144(8) nm, c = 1.2645(3) nm, β = 104.68(1)◦ (for Tb3.33 CuPb1.5 Se7 ); a = 1.3557(5) nm, b = 0.4091(1) nm, c = 1.2574(4) nm, β = 104.59(2)◦ (for Dy3.33 CuPb1.5 Se7 );
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Table 2 Atomic coordinates and temperature factors for the Lu3.33 CuPb1.5 Se7 compound Atom Lu1 Lu2 Lu3 M1 M2 Cu Pb1 Pb2 Se1 Se2 Se3 Se4 Se5 Se6 Se7
Position
x/a
2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a)
0.0000a 0.8806(1) 0.1196(1) 0.7092(6) 0.6635(5) 0.5821(3) 0.3426(5) 0.2944(5) 0.0102(5) 0.2620(5) 0.9807(6) 0.7344(6) 0.3493(5) 0.498(1) 0.6494(5)
y/b
z/c
Occupation
Ueq. × 102 (nm2 )
U11
U22
U33
U23
U13
U12
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.5000a
1.00 1.00 1.00 0.17Lu, 0.25Pb 0.17Lu, 0.25Pb 1.00 0.50 0.50 1.00 1.00 1.00 1.00 1.00 1.00 1.00
0.0152(3) 0.0134(8) 0.0100(8) 0.007(1) 0.012(2) 0.016(1) 0.027(2) 0.020(1) 0.013(1) 0.006(1) 0.023(1) 0.018(2) 0.012(1) 0.032(1) 0.016(2)
0.0203(7) 0.016(1) 0.008(1) 0.005(4) 0.007(4) 0.022(3) 0.028(4) 0.017(4) 0.018(3) 0.013(3) 0.030(4) 0.010(3) 0.019(4) 0.033(1) 0.010(4)
0.0109(6) 0.013(1) 0.012(1) 0.005(4) 0.009(4) 0.019(3) 0.022(4) 0.026(4) 0.003(3) 0.003(3) 0.029(4) 0.024(5) 0.015(4) 0.010(1) 0.013(4)
0.0169(8) 0.007(1) 0.009(1) 0.013(4) 0.025(5) 0.009(3) 0.034(5) 0.016(4) 0.011(4) 0.005(4) 0.006(4) 0.013(5) 0.002(4) 0.066(3) 0.030(6)
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.0097(6) −0.001(1) 0.002(1) 0.002(4) 0.011(4) 0.003(2) 0.013(4) −0.001(4) −0.010(3) 0.007(3) −0.002(3) −0.007(3) 0.001(3) 0.038(1) 0.013(4)
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.0713(2) 0.9313(2) 0.3249(8) 0.3076(9) 0.7141(4) 0.7002(8) 0.6765(7) 0.2849(7) 0.1341(6) 0.7239(8) 0.8654(7) 0.4581(6) 0.000(1) 0.5444(7)
Ueq. is definite as one third of the trace of the orthogonalized Uij tensor. The anisotropic temperature factor exponent takes the form: −2π2 [h2 a∗2 U11 + · · · + 2hka∗ b∗ U12 ]. a Fixed.
a = 1.3425(2) nm, b = 0.40437(4) nm, c = 1.2484(1) nm, β = 104.381(8)◦ (for Yb3.33 CuPb1.5 Se7 ). In the case of the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds a complete crystal structure investigation was performed. According to results of the phase analysis the presence of the peaks of the new Ho3.33 CuPb1.5 Se7 compound and weak additional peaks of the phases HoCuSe2 [1,2] and HoSe2 [13] was observed in the X-ray powder diffraction pattern of the corresponding sample. For this reason the DBWS-9411 program was used for the crystal structure determination. The presence of the HoCuSe2 (ErCu3 S3 ¯ and HoSe2 (Cu2 Sb structure structure type, space group P 3) type, space group P4/nmm) phases was taken into account during the refinement procedure of the Ho3.33 CuPb1.5 Se7
compound. The presence of ErCuSe2 (ErCu3 S3 structure ¯ [1,2] and TmCuSe2 (ErCu3 S3 type, space group P 3) ¯ [1,2], Tm2 Se2 (Sc2 S3 structure type, space group P 3) structure type, space group Fddd) [14] as minority phases was taken into account during the refinement procedure of the Er3.33 CuPb1.5 Se7 and Tm3.33 CuPb1.5 Se7 compounds, respectively. Table 3 contains the essential technical and crystallographic data of the crystal structure determination of the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds. Atomic coordinates are listed in Table 4. The following overall temperature factors for all atoms were determined during the refinement procedure: B = 1.30(7) × 10−2 nm2 (for Ho3.33 CuPb1.5 Se7 ), B = 0.69(6) × 10−2 nm2 (for Er3.33 CuPb1.5 Se7 ), B = 0.54(7) × 10−2 nm2 (for
Table 3 Crystal data and structure refinement details of the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds Empirical formula Formula weight Space group Unit cell dimensions Volume Number of formula units per unit cell Calculated density Absorption coefficient F(0 0 0) Diffractometer 2Θ range for data collection Refinement method RI RP Preferred orientation Preferred orientation parameter a b c
Ho3.33 CuPb1.5 Se7 1476.83 Cm (No. 8) a = 1.35314(8) nm, b = 0.40819(2) nm, c = 1.25609(7) nm, β = 104.577(3)◦ 0.6715(1) nm3 2
Er3.33 CuPb1.5 Se7 1484.59 Cm (No. 8) a = 1.35018(7) nm, b = 0.40693(2) nm, c = 1.25433(6) nm, β = 104.492(2)◦ 0.6672(1) nm3 2
Tm3.33 CuPb1.5 Se7 1490.17 Cm (No. 8) a = 1.34584(7) nm, b = 0.40560(2) nm, c = 1.25083(6) nm, β = 104.342(3)◦ 0.6615(1) nm3 2
7.305 g/cm3 97.127 mm−1 1226 Powder DRON-4-13 10.00–100.00
7.390 g/cm3 99.901 mm−1 1233 Powder DRON-4-13 10.00–100.00
7.482 g/cm3 102.837 mm−1 1240 Powder DRON-4-13 10.00–100.00
Full profile 0.0797 0.0262a [1 0 1] 0.029(8)
Full profile 0.0845 0.0311b [1 0 1] 0.157(8)
Full profile 0.0866 0.0303c [1 0 1] 0.139(8)
Presence of HoCuSe2 and HoSe2 as additional phases was taken into account during the refinement procedure. Presence of ErCuSe2 as additional phase was taken into account during the refinement procedure. Presence of TmCuSe2 and Tm2 Se2 as additional phases was taken into account during the refinement procedure.
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Fig. 1. The experimental and calculated diffractograms and the corresponding difference diagram for Ho3.33 CuPb1.5 Se7 (1-Ho3.33 CuPb1.5 Se7 , 2-HoCuSe2 , 3-HoSe2 ).
Tm3.33 CuPb1.5 Se7 ). The experimental and calculated diffractograms and the corresponding difference diagram for Ho3.33 CuPb1.5 Se7 (1-Ho3.33 CuPb1.5 Se7 , 2-HoCuSe2 , 3-HoSe2 ) are shown in Fig. 1. The relevant interatomic distances (δ, nm) and coordination numbers (C.N.) of the atoms in the R3.33 CuPb1.5 Se7 (R = Ho, Er, Tm and Lu) compounds are listed in Table 5. The interatomic distances agree well with the sum of the corresponding ionic radii [15]. The unit cell and coordination polyhedra of the Lu1 (a), Lu2 (b), Lu3 (c), M1 (Lu + Pb) (d), M2 (Lu + Pb) (e) Cu (f), Pb1 (g), Pb2 (h), Se1 (i), Se2 (j), Se3 (k), Se4 (l), Se5 (m), Se6 (n), Se7 (o) atoms in the structure of the Lu3.33 CuPb1.5 Se7
compound are shown in Fig. 2. The Lu atoms are surrounded by octahedra. The atoms of the statistical mixtures M1 and M2 (Lu + Pb) and the Pb1 and Pb2 atoms are surrounded by trigonal prisms with one additional atom. A tetrahedral surrounding exists for the Cu atoms. Since the positions of the atoms of the statistical mixtures M1, M2 (0.17Lu + 0.25Pb) and the Pb1, Pb2 (0.50Pb) atoms are partially occupied such coordination numbers of the Se-centred polyhedra really exist: Se1 (C.N. = 4), Se2 (C.N. = 5), Se3 (C.N. = 6), Se4 (C.N. = 6), Se5 (C.N. = 5), Se6 (C.N. = 4), Se7 (C.N. = 6). The atoms of the statistical mixtures M1, M2 (Lu + Pb) and the Pb1, Pb2 atoms are located in trigonal prisms with one additional atom. The same Se atoms (see Table 5) form
Table 4 Atomic coordinates for the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds Atom
Position
Occupation
Ho3.33 CuPb1.5 Se7
Er3.33 CuPb1.5 Se7
Tm3.33 CuPb1.5 Se7
R1 R2 R3 M1 M2 Cu Pb1 Pb2 Se1 Se2 Se3 Se4 Se5 Se6 Se7
2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z
1.00 1.00 1.00 0.17R, 0.25Pb 0.17R, 0.25Pb 1.00 0.50 0.50 1.00 1.00 1.00 1.00 1.00 1.00 1.00
x = 0.000a , z = 0.500a x = 0.888(2), z = 0.066(2) x = 0.120(2), z = 0.923(2) x = 0.692(3), z = 0.323(4) x = 0.673(3), z = 0.319(4) x = 0.587(2), z = 0.707(2) x = 0.319(3), z = 0.700(3) x = 0.304(3), z = 0.670(2) x = 0.017(3), z = 0.283(3) x = 0.257(2), z = 0.129(3) x = 0.980(3), z = 0.720(3) x = 0.727(2), z = 0.858(3) x = 0.343(2), z = 0.450(2) x = 0.497(3), z = 0.995(4) x = 0.639(2), z = 0.546(2)
x = 0.000a , z = 0.500a x = 0.887(1), z = 0.071(2) x = 0.121(1), z = 0.927(2) x = 0.693(4), z = 0.318(4) x = 0.686(3), z = 0.332(3) x = 0.583(2), z = 0.711(2) x = 0.343(2), z = 0.701(2) x = 0.295(3), z = 0.682(2) x = 0.018(2), z = 0.285(2) x = 0.262(2), z = 0.134(3) x = 0.981(2), z = 0.722(2) x = 0.733(2), z = 0.865(3) x = 0.342(2), z = 0.451(2) x = 0.505(3), z = 0.989(2) x = 0.642(2), z = 0.545(2)
x = 0.000a , z = 0.500a x = 0.892(1), z = 0.072(2) x = 0.131(1), z = 0.931(1) x = 0.706(4), z = 0.322(5) x = 0.684(4), z = 0.324(5) x = 0.585(2), z = 0.713(2) x = 0.349(2), z = 0.707(2) x = 0.299(3), z = 0.678(2) x = 0.011(3), z = 0.289(2) x = 0.273(3), z = 0.145(3) x = 0.985(3), z = 0.730(2) x = 0.751(3), z = 0.876(3) x = 0.352(2), z = 0.456(3) x = 0.509(2), z = 0.025(2) x = 0.642(2), z = 0.547(3)
a
Fixed.
L.D. Gulay, I.D. Olekseyuk / Journal of Alloys and Compounds 396 (2005) 233–239
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Table 5 Interatomic distances (δ, nm) and coordination numbers (C.N.) of the atoms in the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds Atoms
δ (nm)
C.N.
Ho3.33 CuPb1.5 Se7
Er3.33 CuPb1.5 Se7
Tm3.33 CuPb1.5 Se7
Lu3.33 CuPb1.5 Se7
R1–2Se7 R1–1Se1 R1–1Se3 R1–2Se5
0.273 0.279 0.284 0.289
0.275 0.276 0.286 0.290
0.274 0.268 0.293 0.280
0.2798 0.2721 0.2868 0.2809
6
R2–2Se6 R2–1Se1 R2–2Se2 R2–1Se4
0.279(4) 0.284(5) 0.294(3) 0.295(4)
0.293(3) 0.282(3) 0.288(2) 0.288(4)
0.272(2) 0.279(4) 0.287(3) 0.270(4)
0.283(1) 0.2797(9) 0.2796(5) 0.2818(9)
6
R3–2Se4 R3–1Se3 R3–1Se2 R3–2Se6
0.274(3) 0.277(5) 0.278(4) 0.292(4)
0.276(2) 0.278(3) 0.281(4) 0.279(3)
0.278(3) 0.278(3) 0.288(4) 0.302(2)
0.2781(6) 0.278(1) 0.2766(8) 0.285(1)
6
M1–2Se5 M1–1Se7 M1–2Se1 M1–2Se2
0.304(4) 0.306(5) 0.307(5) 0.346(5)
0.305(4) 0.309(6) 0.307(5) 0.338(5)
0.303(5) 0.314(7) 0.326(5) 0.329(6)
0.2967(9) 0.303(1) 0.3281(9) 0.332(1)
7
M2–2Se1 M2–1Se7 M2–2Se5 M2–2Se2
0.289(4) 0.300(5) 0.320(4) 0.354(5)
0.299(4) 0.288(5) 0.304(4) 0.355(4)
0.304(5) 0.298(7) 0.318(5) 0.345(6)
0.2842(7) 0.300(1) 0.3387(9) 0.345(1)
7
Cu–1Se7 Cu–1Se4 Cu–2Se3
0.230(4) 0.232(4) 0.253(3)
0.241(4) 0.242(4) 0.248(2)
0.239(4) 0.263(5) 0.247(3)
0.249(1) 0.241(1) 0.2451(6)
4
Pb1–2Se3 Pb1–1Se5 Pb1–2Se4 Pb1–2Se7
0.295(4) 0.324(5) 0.330(4) 0.339(4)
0.273(3) 0.313(4) 0.348(3) 0.356(3)
0.270(3) 0.315(4) 0.342(4) 0.362(3)
0.2703(8) 0.304(1) 0.344(1) 0.3471(9)
7
Pb2–1Se5 Pb2–2Se3 Pb2–2Se7 Pb2–2Se4
0.294(4) 0.308(4) 0.313(3) 0.347(4)
0.312(4) 0.317(3) 0.310(3) 0.333(3)
0.303(5) 0.316(4) 0.309(4) 0.338(4)
0.299(1) 0.3149(9) 0.2994(8) 0.334(1)
7
Se1–1R1 Se1–1R2 Se1–2M2 Se1–2M1
0.279 0.284(5) 0.289(4) 0.307(5)
0.276 0.282(3) 0.299(4) 0.307(5)
0.268 0.279(4) 0.304(5) 0.326(5)
0.2721 0.2797(9) 0.2842(7) 0.3281(9)
6-2
Se2–1R3 Se2–2R2 Se2–2M1 Se2–2M2
0.278(4) 0.294(3) 0.346(5) 0.354(5)
0.281(4) 0.288(2) 0.338(5) 0.355(4)
0.288(4) 0.287(3) 0.329(6) 0.345(6)
0.2766(8) 0.2796(5) 0.332(1) 0.345(1)
7-2
Se3–2Cu Se3–1R3 Se3–1R1 Se3–2Pb1 Se3–2Pb2
0.253(3) 0.277(5) 0.284 0.295(4) 0.308(4)
0.248(2) 0.278(3) 0.286 0.273(3) 0.317(3)
0.247(3) 0.278(3) 0.293 0.270(3) 0.316(4)
0.2451(6) 0.278(1) 0.2868 0.2703(8) 0.3149(9)
8-2
Se4–1Cu Se4–2R3 Se4–1R2 Se4–2Pb1 Se4–2Pb2
0.232(4) 0.274(3) 0.295(4) 0.330(4) 0.347(4)
0.242(4) 0.276(2) 0.288(4) 0.348(3) 0.333(3)
0.263(5) 0.278(3) 0.270(4) 0.342(4) 0.338(4)
0.241(1) 0.2781(6) 0.2818(9) 0.344(1) 0.334(1)
8-2
Se5–2R1 Se5–1Pb2 Se5–2M1 Se5–2M2 Se5–1Pb1
0.289 0.294(4) 0.304(4) 0.320(4) 0.324(5)
0.290 0.312(4) 0.305(4) 0.304(4) 0.313(4)
0.280 0.303(5) 0.303(5) 0.318(5) 0.315(4)
0.2809 0.299(1) 0.2967(9) 0.3387(9) 0.304(1)
8-3
Se6–2R2
0.279(4)
0.293(3)
0.272(2)
0.283(1)
4
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Table 5 (Continud ) Atoms
δ (nm) Ho3.33 CuPb1.5 Se7
Er3.33 CuPb1.5 Se7
Tm3.33 CuPb1.5 Se7
Lu3.33 CuPb1.5 Se7
Se6–2R3
0.292(4)
0.279(3)
0.302(2)
0.285(1)
Se7–1Cu Se7–2R1 Se7–1M2 Se7–1M1 Se7–2Pb2 Se7–2Pb1
0.230(4) 0.273 0.300(5) 0.306(5) 0.313(3) 0.339(4)
0.241(4) 0.275 0.288(5) 0.309(6) 0.310(3) 0.356(3)
0.239(4) 0.274 0.298(7) 0.314(7) 0.309(4) 0.362(3)
0.249(1) 0.2798 0.300(1) 0.303(1) 0.2994(8) 0.3471(9)
C.N.
trigonal prisms for M1 (M2) and Pb1 (Pb2). The atoms of the statistical mixtures M1 (M2) and the Pb1 (Pb2) atoms are slightly shifted from the centers of corresponding prisms. The M1 + M2- and Pb1 + Pb2-centered trigonal prisms as combination of the M1-, M2- and Pb1-, Pb2-centered trigonal prisms in the structure of the Lu3.33 CuPb1.5 Se7 compound are shown in Fig. 3. The crystal structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds can be derived from the structure of the binary Y5 Se7 compound [16]. The positions of the Y (R) atoms with octahedral coordination in the binary Y5 Se7 compound and quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds are similar. Every position of the Y atom with trigonal prismatic coordination in the Y5 Se7 compound corresponds to two defect positions of the atoms of the statistical mixture M (R + Pb) or Pb in the structures of the R3.33 CuPb1.5 Se7
9-3
Table 6 The relations between the crystal structures of the compounds Y5 Se7 and Lu3.33 CuPb1.5 Se7 Y5 Se7 Space group Cm a = 1.3213 nm b = 0.39490 nm c = 1.2035 nm β = 104.82◦ Y1 2(a) x 0 z; x = 0.000, z = 0.500 Y2 2(a) x 0 z; x = 0.6928, z = 0.3095 Y3 2(a) x 0 z; x = 0.8829, z = 0.0786 Y4 2(a) x 0 z; x = 0.1119, z = 0.9259 Y5 2(a) x 0 z; x = 0.3012, z = 0.6951 Se1 2(a) x 0 z; x = 0.0376, z = 0.2857 Se2 2(a) x 0 z; x = 0.2597, z = 0.1509 Se3 2(a) x 0 z; x = 0.9620, z = 0.7185 Se4 2(a) x 0 z; x = 0.7400, z = 0.8538 Se5 2(a) x 0 z; x = 0.3400, z = 0.4523 Se6 2(a) x 0 z; x = 0.5106, z = 0.0182 Se7 2(a) x 0 z; x = 0.6598, z = 0.5532
Lu3.33 CuPb1.5 Se7 Space group Cm a = 1.3404 nm b = 0.40307 nm c = 1.2475 nm β = 104.36◦ Lu1 2(a) x 0 z; x = 0.0000, z = 0.5000 M1 2(a) x 0 z; x = 0.7092, z = 0.3249 M2 2(a) x 0 z; x = 0.6635, z = 0.3076 Lu2 2(a) x 0 z; x = 0.8806, z = 0.0713 Lu3 2(a) x 0 z; x = 0.1196, z = 0.9313 Pb1 2(a) x 0 z; x = 0.3426, z = 0.7002 Pb2 2(a) x 0 z; x = 0.2944, z = 0.6765 Se1 2(a) x 0 z; x = 0.0102, z = 0.2849 Se2 2(a) x 0 z; x = 0.2620, z = 0.1341 Se3 2(a) x 0 z; x = 0.9807, z = 0.7239 Se4 2(a) x 0 z; x = 0.7344, z = 0.8654 Se5 2(a) x 0 z; x = 0.3493, z = 0.4581 Se6 2(a) x 0 z; x = 0.498, z = 0.000 Se7 2(a) x 0 z; x = 0.6494, z = 0.5444 Cu 2(a) x 0 z; x = 0.5821, z = 0.7141
(R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds. An additional position of the Cu atoms with tetrahedral coordination exists in the structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds when compared with Y5 Se7 . The relation between the crystal structures of the compounds Y5 Se7 and Lu3.33 CuPb1.5 Se7 is described in Table 6.
Fig. 2. The unit cell and coordination polyhedra of the Lu1 (a), Lu2 (b), Lu3 (c), M1 (Lu + Pb) (d), M2 (Lu + Pb) (e), Cu (f), Pb1 (g), Pb2 (h), Se1 (i), Se2 (j), Se3 (k), Se4 (l), Se5 (m), Se6 (n), Se7 (o) atoms in the structure of the Lu3.33 CuPb1.5 Se7 compound.
Fig. 3. The M1 + M2- and Pb1 + Pb2-centered trigonal prisms as combination of the M1-, M2- and Pb1-, Pb2-centered trigonal prisms in the structure of the Lu3.33 CuPb1.5 Se7 compound.
L.D. Gulay, I.D. Olekseyuk / Journal of Alloys and Compounds 396 (2005) 233–239
Acknowledgement The authors are grateful to Prof. A. Pietraszko (W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wrocław, Poland) for the assistance in single crystal data collection.
[6] [7] [8] [9] [10] [11]
References [12] [1] M. Julien-Pouzol, M. Guittard, J. Flahaut, Bull. Soc. Chim. France (1968) 533. [2] M. Julien-Pouzol, M. Guittard, Ann. Chim. 7 (1972) 253. [3] M. Julien-Pouzol, M. Guittard, Bull. Soc. Chim. France (1968) 2293. [4] M. Patrie, M. Guittard, M.-P. Pardo, Bull. Soc. Chim. France (1969) 3832. [5] L.D. Gulay, V.Ya. Shemet, I.D. Olekseyuk, J. Alloys Comp. 385 (2004) 160.
[13] [14] [15] [16]
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S. Strobel, Th. Schleid, J. Solid State Chem. 171 (2003) 424. L.D. Gulay, I.D. Olekseyuk, J. Alloys Comp. 387 (2005) 154. L.D. Gulay, I.D. Olekseyuk, J. Alloys Comp. 387 (2005) 160. G.M. Sheldrick, Program for the Solution of Crystal Structures, University of G¨ottingen, Germany, 1985. G.M. Sheldrick, Program for Crystal Structures Refinement, University of G¨ottingen, Germany, 1997. R.A. Young, A. Sakthivel, T.S. Moss, C.O. Paria-Santos, Program DBWS-9411 for Rietveld Analysis of X-ray and Neutron Powder Diffraction Patterns, Georgia Institute of Technology, Atlanta, GA, 1995. L.D. Gulay, V.Ya. Shemet, I.D. Olekseyuk, J. Alloys Comp 394 (2005) 250. R. Wang, H. Steinfink, Inorg. Chem. 6 (1967) 1685. J. Flahaut, P. Laruelle, M.P. Pardo, M. Guittard, Bull. Soc. Chim. France (1965) 1399. N. Wiberg, Lehrbuch der Anorganischen Chemie, Walter de Gruyter, Berlin, 1995, pp. 1838–1841. S.-J. Kim, H.F. Franzen, J. Less-Common Met. 138 (1988) L29.
Crystal structures of the R3.33CuPb1.5Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds L.D. Gulay ∗ , I.D. Olekseyuk Department of General and Inorganic Chemistry, Volyn State University, Voli Ave 13, 43009 Lutsk, Ukraine Received 18 December 2004; accepted 4 January 2005 Available online 10 February 2005
Abstract The crystal structures of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds (space group Cm, Pearson symbol mC25.67) were determined by means of X-ray powder diffraction: a = 1.3624(3) nm, b = 0.41144(8) nm, c = 1.2645(3) nm, β = 104.68(1)◦ (for Tb3.33 CuPb1.5 Se7 ); a = 1.3557(5) nm, b = 0.4091(1) nm, c = 1.2574(4) nm, β = 104.59(2)◦ (for Dy3.33 CuPb1.5 Se7 ); a = 1.35314(8) nm, b = 0.40819(2) nm, c = 1.25609(7) nm, β = 104.577(3)◦ , RI = 0.0797 (for Ho3.33 CuPb1.5 Se7 ); a = 1.35018(7) nm, b = 0.40693(2) nm, c = 1.25433(6) nm, β = 104.492(2)◦ , RI = 0.0845 (for Er3.33 CuPb1.5 Se7 ); a = 1.34584(7) nm, b = 0.40560(2) nm, c = 1.25083(6) nm, β = 104.342(3)◦ , RI = 0.0866 (for Tm3.33 CuPb1.5 Se7 ); a = 1.3425(2) nm, b = 0.40437(4) nm, c = 1.2484(1) nm, β = 104.381(8)◦ (for Yb3.33 CuPb1.5 Se7 ) and single crystal diffraction: a = 1.3404(2) nm, b = 0.40307(6) nm, c = 1.2475(2) nm, β = 104.36(1)◦ , R1 = 0.0438 (for Lu3.33 CuPb1.5 Se7 ). The crystal structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds can be derived from the structure of the binary Y5 Se7 compound. The positions of the Y (R) atoms with octahedral coordination in the binary Y5 Se7 compound and the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds are similar. Every position of the Y atom with trigonal prismatic coordination in the Y5 Se7 compound corresponds to two defect positions of the atoms of the statistical mixture M (R + Pb) or Pb in the structures of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds. Additional position of the Cu atoms with tetrahedral coordination exists in the structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds when compared with Y5 Se7 . © 2005 Elsevier B.V. All rights reserved. Keywords: Chalcogenides; Rare earth compounds; Cu compounds; Pb compounds; Se compounds; Crystal structure; X-ray single crystal diffraction; X-ray powder diffraction
1. Introduction The existence of the compounds with the compositions RCuSe2 R2/3 Cu2 Se2 (R = Sc, Y, Tb, Dy, Ho, Er, Tm, Yb and Lu) and GdCu3 Se3 (ErCu3 S3 structure type, space group ¯ has been reported in Refs. [1,2]. According to Ref. [2] P 3) the RCuSe2 (R = La, Ce, Pr, Nd, Sm and Gd) compounds adopt the LaCuS2 structure type (space group P21 /c). The R2 Se3 R5 CuSe8 (R = La, Ce, Pr, Nd, Sm and Gd) solid so¯ have been lutions (Th3 P4 structure type, space group I43d) ∗
Corresponding author. E-mail address: [email protected] (L.D. Gulay).
0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2005.01.014
established in Refs. [2,3]. The orthorhombic unit cell has been found for the compound with the composition La5 Cu13 Se14 [2]. The existence of the R2 Se3 R2 PbSe4 (R = La, Ce, Pr, Nd and Sm) solid solutions with Th3 P4 structure type (space ¯ group I43d) and the R2 PbSe4 (R = Er, Tm, Yb and Lu) compounds with CaFe2 O4 structure type (space group Pnma) has been reported in Ref. [4]. The Gd(Tb)2 Se3 based solid ¯ in the solutions (Th3 P4 structure type, space group I43d) Gd(Tb)2 Se3 PbSe systems has been also established in Ref. [4]. The existence of the Y3 Cu0.685 Se6 [5], Sm3 CuSe6 [6], R3 CuSe6 (R = Gd, Tb and Dy) [7] compounds (Sm3 CuSe6 structure type, space group Pbcm) has been established recently. The crystal structures of the RCuPbSe3 (R = Y, Gd, Tb,
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Dy, Ho, Er, Tm, Yb and Lu) (-BaLaCuSe3 structure type, space group Pnma) have been determined in Refs. [5,8]. The crystal structures of new quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds are given in the present paper.
Table 1 Crystal data and structure refinement details of the Lu3.33 CuPb1.5 Se7 compound
2. Experimental details
Volume Number of formula units per unit cell Calculated density Absorption coefficient F(0 0 0) Crystal size Θ range for data collection Index ranges
The samples were prepared by melting the high purity starting elements (the purity of the ingredients was better than 99.9 wt.%) in evacuated quartz ampoules. The synthesis was realized in a shaft furnace. The ampoules were heated with a heating rate of 30 K/h to the maximal temperature, 1420 K. The samples were kept at the 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. A single crystal of the Lu3.33 CuPb1.5 Se7 compound was selected from the sample of the corresponding composition for a crystal structure determination. The X-ray intensity data were collected on a KUMA diffraction KM-4 fourcircle single crystal diffractometer equipped with a CCD camera using graphite-monochromatized Mo K␣ radiation (λ = 0.071073 nm). The intensities of the reflections were corrected for Lorentz and polarisation factors. A semiempirical absorption correction was applied. The crystal structure was solved by Patterson methods [9] and refined by a full matrix least squares method using the SHELX-97 program [10]. X-ray powder diffraction patterns of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm and Yb) compounds for the crystal structure determination were recorded using a DRON4-13 (Cu K␣ radiation, 10◦ ≤ 2Θ ≤ 100◦ , step scan mode with a step size of 0.05◦ and counting time of 20 s per data point). Crystal structure determination was performed using the DBWS-9411 [11] program.
3. Results and discussion The formation of new quaternary R3.33 CuPb1.5 Se7 compounds was observed during the investigation of the phase relations in the R2 Se3 Cu2 Se PbSe (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) systems. The similarity of the X-ray powder diffraction patterns of these compounds allows us to conclude that they are isostructural. A good quality single crystal of the Lu3.33 CuPb1.5 Se7 compound was selected from the sample of the corresponding composition. The extinctions were found to be consistent with the centrosymmetric space group C2/m and the non-centrosymmetric space group Cm. Refinements were performed within both space groups. Similar structural models were obtained. Some difference was observed for the positions of the Cu atoms. A better structural model was obtained in case of the noncentrosymmetric space group Cm. The crystal data and the
Empirical formula Formula weight Space group Unit cell dimensions
Reflections collected Independent reflections Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I > 2σ(I)] R indices (all data) Extinction coefficient Largest diffraction peak and hole ×10−3
Lu3.33 CuPb1.5 Se7 1510.56 Cm (No. 8) a = 1.3404(2) nm, b = 0.40307(6) nm, c = 1.2475(2) nm, β = 104.36(1)◦ 0.6529(2) nm3 2 7.683 g/cm3 65.297 mm−1 1254 0.07 mm × 0.08 mm × 0.15 mm 3.15–27.10 −17 ≤ h ≤ 18, −5 ≤ k ≤ 5, −17 ≤ l ≤ 16 3973 1780 [R(int.) = 0.0802] Full-matrix least-square on F2 1780/0/90 1.011 R1 = 0.0438, wR2 = 0.0775 R1 = 0.0803, wR2 = 0.0879 0.00155(7) 3.121 and −3.080 electrons/nm3
refinement information are summarized in Table 1. The final atomic coordinates and temperature factors are given in Table 2. At the first stage, one position of the atoms of the statistical mixture M (0.33Lu + 0.50Pb) and one position of the Pb atoms with occupation factor 1.00 were determined for the Lu3.33 CuPb1.5 Se7 compound similar to the structure of the Y3.33 CuPb1.5 Se7 compound reported in our recent paper [12]. Unusual values of the anisotropic thermal parameters for the atoms of the statistical mixture M (0.33Lu + 0.50Pb), the Pb atoms and a residual electron density of about 11 electrons/10−3 nm3 near those atoms were observed at this stage. At the second stage the positions of the atoms of the statistical mixture M (0.33Lu + 0.50Pb) were split into two close positions M1 (0.17Lu + 0.25Pb) and M2 (0.17Lu + 0.25Pb). The Pb atoms were also located in two close positions with occupation factors 0.50. At this stage the anisotropic thermal parameters for the atoms of the statistical mixtures M1, M2 and the Pb1, Pb2 atoms were significantly reduced. The final value of R1 factor was improved significantly from 0.0685 to 0.0438. The crystal structures of the R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm and Yb) compounds were investigated using X-ray powder diffraction. X-ray powder diffraction patterns of the R3.33 CuPb1.5 Se7 (R = Tb, Dy and Yb) samples were not of good quality for a reliable crystal structure investigation. Only lattice parameters were determined for those compounds: a = 1.3624(3) nm, b = 0.41144(8) nm, c = 1.2645(3) nm, β = 104.68(1)◦ (for Tb3.33 CuPb1.5 Se7 ); a = 1.3557(5) nm, b = 0.4091(1) nm, c = 1.2574(4) nm, β = 104.59(2)◦ (for Dy3.33 CuPb1.5 Se7 );
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Table 2 Atomic coordinates and temperature factors for the Lu3.33 CuPb1.5 Se7 compound Atom Lu1 Lu2 Lu3 M1 M2 Cu Pb1 Pb2 Se1 Se2 Se3 Se4 Se5 Se6 Se7
Position
x/a
2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a) 2(a)
0.0000a 0.8806(1) 0.1196(1) 0.7092(6) 0.6635(5) 0.5821(3) 0.3426(5) 0.2944(5) 0.0102(5) 0.2620(5) 0.9807(6) 0.7344(6) 0.3493(5) 0.498(1) 0.6494(5)
y/b
z/c
Occupation
Ueq. × 102 (nm2 )
U11
U22
U33
U23
U13
U12
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.5000a
1.00 1.00 1.00 0.17Lu, 0.25Pb 0.17Lu, 0.25Pb 1.00 0.50 0.50 1.00 1.00 1.00 1.00 1.00 1.00 1.00
0.0152(3) 0.0134(8) 0.0100(8) 0.007(1) 0.012(2) 0.016(1) 0.027(2) 0.020(1) 0.013(1) 0.006(1) 0.023(1) 0.018(2) 0.012(1) 0.032(1) 0.016(2)
0.0203(7) 0.016(1) 0.008(1) 0.005(4) 0.007(4) 0.022(3) 0.028(4) 0.017(4) 0.018(3) 0.013(3) 0.030(4) 0.010(3) 0.019(4) 0.033(1) 0.010(4)
0.0109(6) 0.013(1) 0.012(1) 0.005(4) 0.009(4) 0.019(3) 0.022(4) 0.026(4) 0.003(3) 0.003(3) 0.029(4) 0.024(5) 0.015(4) 0.010(1) 0.013(4)
0.0169(8) 0.007(1) 0.009(1) 0.013(4) 0.025(5) 0.009(3) 0.034(5) 0.016(4) 0.011(4) 0.005(4) 0.006(4) 0.013(5) 0.002(4) 0.066(3) 0.030(6)
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.0097(6) −0.001(1) 0.002(1) 0.002(4) 0.011(4) 0.003(2) 0.013(4) −0.001(4) −0.010(3) 0.007(3) −0.002(3) −0.007(3) 0.001(3) 0.038(1) 0.013(4)
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0.0713(2) 0.9313(2) 0.3249(8) 0.3076(9) 0.7141(4) 0.7002(8) 0.6765(7) 0.2849(7) 0.1341(6) 0.7239(8) 0.8654(7) 0.4581(6) 0.000(1) 0.5444(7)
Ueq. is definite as one third of the trace of the orthogonalized Uij tensor. The anisotropic temperature factor exponent takes the form: −2π2 [h2 a∗2 U11 + · · · + 2hka∗ b∗ U12 ]. a Fixed.
a = 1.3425(2) nm, b = 0.40437(4) nm, c = 1.2484(1) nm, β = 104.381(8)◦ (for Yb3.33 CuPb1.5 Se7 ). In the case of the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds a complete crystal structure investigation was performed. According to results of the phase analysis the presence of the peaks of the new Ho3.33 CuPb1.5 Se7 compound and weak additional peaks of the phases HoCuSe2 [1,2] and HoSe2 [13] was observed in the X-ray powder diffraction pattern of the corresponding sample. For this reason the DBWS-9411 program was used for the crystal structure determination. The presence of the HoCuSe2 (ErCu3 S3 ¯ and HoSe2 (Cu2 Sb structure structure type, space group P 3) type, space group P4/nmm) phases was taken into account during the refinement procedure of the Ho3.33 CuPb1.5 Se7
compound. The presence of ErCuSe2 (ErCu3 S3 structure ¯ [1,2] and TmCuSe2 (ErCu3 S3 type, space group P 3) ¯ [1,2], Tm2 Se2 (Sc2 S3 structure type, space group P 3) structure type, space group Fddd) [14] as minority phases was taken into account during the refinement procedure of the Er3.33 CuPb1.5 Se7 and Tm3.33 CuPb1.5 Se7 compounds, respectively. Table 3 contains the essential technical and crystallographic data of the crystal structure determination of the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds. Atomic coordinates are listed in Table 4. The following overall temperature factors for all atoms were determined during the refinement procedure: B = 1.30(7) × 10−2 nm2 (for Ho3.33 CuPb1.5 Se7 ), B = 0.69(6) × 10−2 nm2 (for Er3.33 CuPb1.5 Se7 ), B = 0.54(7) × 10−2 nm2 (for
Table 3 Crystal data and structure refinement details of the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds Empirical formula Formula weight Space group Unit cell dimensions Volume Number of formula units per unit cell Calculated density Absorption coefficient F(0 0 0) Diffractometer 2Θ range for data collection Refinement method RI RP Preferred orientation Preferred orientation parameter a b c
Ho3.33 CuPb1.5 Se7 1476.83 Cm (No. 8) a = 1.35314(8) nm, b = 0.40819(2) nm, c = 1.25609(7) nm, β = 104.577(3)◦ 0.6715(1) nm3 2
Er3.33 CuPb1.5 Se7 1484.59 Cm (No. 8) a = 1.35018(7) nm, b = 0.40693(2) nm, c = 1.25433(6) nm, β = 104.492(2)◦ 0.6672(1) nm3 2
Tm3.33 CuPb1.5 Se7 1490.17 Cm (No. 8) a = 1.34584(7) nm, b = 0.40560(2) nm, c = 1.25083(6) nm, β = 104.342(3)◦ 0.6615(1) nm3 2
7.305 g/cm3 97.127 mm−1 1226 Powder DRON-4-13 10.00–100.00
7.390 g/cm3 99.901 mm−1 1233 Powder DRON-4-13 10.00–100.00
7.482 g/cm3 102.837 mm−1 1240 Powder DRON-4-13 10.00–100.00
Full profile 0.0797 0.0262a [1 0 1] 0.029(8)
Full profile 0.0845 0.0311b [1 0 1] 0.157(8)
Full profile 0.0866 0.0303c [1 0 1] 0.139(8)
Presence of HoCuSe2 and HoSe2 as additional phases was taken into account during the refinement procedure. Presence of ErCuSe2 as additional phase was taken into account during the refinement procedure. Presence of TmCuSe2 and Tm2 Se2 as additional phases was taken into account during the refinement procedure.
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Fig. 1. The experimental and calculated diffractograms and the corresponding difference diagram for Ho3.33 CuPb1.5 Se7 (1-Ho3.33 CuPb1.5 Se7 , 2-HoCuSe2 , 3-HoSe2 ).
Tm3.33 CuPb1.5 Se7 ). The experimental and calculated diffractograms and the corresponding difference diagram for Ho3.33 CuPb1.5 Se7 (1-Ho3.33 CuPb1.5 Se7 , 2-HoCuSe2 , 3-HoSe2 ) are shown in Fig. 1. The relevant interatomic distances (δ, nm) and coordination numbers (C.N.) of the atoms in the R3.33 CuPb1.5 Se7 (R = Ho, Er, Tm and Lu) compounds are listed in Table 5. The interatomic distances agree well with the sum of the corresponding ionic radii [15]. The unit cell and coordination polyhedra of the Lu1 (a), Lu2 (b), Lu3 (c), M1 (Lu + Pb) (d), M2 (Lu + Pb) (e) Cu (f), Pb1 (g), Pb2 (h), Se1 (i), Se2 (j), Se3 (k), Se4 (l), Se5 (m), Se6 (n), Se7 (o) atoms in the structure of the Lu3.33 CuPb1.5 Se7
compound are shown in Fig. 2. The Lu atoms are surrounded by octahedra. The atoms of the statistical mixtures M1 and M2 (Lu + Pb) and the Pb1 and Pb2 atoms are surrounded by trigonal prisms with one additional atom. A tetrahedral surrounding exists for the Cu atoms. Since the positions of the atoms of the statistical mixtures M1, M2 (0.17Lu + 0.25Pb) and the Pb1, Pb2 (0.50Pb) atoms are partially occupied such coordination numbers of the Se-centred polyhedra really exist: Se1 (C.N. = 4), Se2 (C.N. = 5), Se3 (C.N. = 6), Se4 (C.N. = 6), Se5 (C.N. = 5), Se6 (C.N. = 4), Se7 (C.N. = 6). The atoms of the statistical mixtures M1, M2 (Lu + Pb) and the Pb1, Pb2 atoms are located in trigonal prisms with one additional atom. The same Se atoms (see Table 5) form
Table 4 Atomic coordinates for the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds Atom
Position
Occupation
Ho3.33 CuPb1.5 Se7
Er3.33 CuPb1.5 Se7
Tm3.33 CuPb1.5 Se7
R1 R2 R3 M1 M2 Cu Pb1 Pb2 Se1 Se2 Se3 Se4 Se5 Se6 Se7
2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z 2(a) x 0 z
1.00 1.00 1.00 0.17R, 0.25Pb 0.17R, 0.25Pb 1.00 0.50 0.50 1.00 1.00 1.00 1.00 1.00 1.00 1.00
x = 0.000a , z = 0.500a x = 0.888(2), z = 0.066(2) x = 0.120(2), z = 0.923(2) x = 0.692(3), z = 0.323(4) x = 0.673(3), z = 0.319(4) x = 0.587(2), z = 0.707(2) x = 0.319(3), z = 0.700(3) x = 0.304(3), z = 0.670(2) x = 0.017(3), z = 0.283(3) x = 0.257(2), z = 0.129(3) x = 0.980(3), z = 0.720(3) x = 0.727(2), z = 0.858(3) x = 0.343(2), z = 0.450(2) x = 0.497(3), z = 0.995(4) x = 0.639(2), z = 0.546(2)
x = 0.000a , z = 0.500a x = 0.887(1), z = 0.071(2) x = 0.121(1), z = 0.927(2) x = 0.693(4), z = 0.318(4) x = 0.686(3), z = 0.332(3) x = 0.583(2), z = 0.711(2) x = 0.343(2), z = 0.701(2) x = 0.295(3), z = 0.682(2) x = 0.018(2), z = 0.285(2) x = 0.262(2), z = 0.134(3) x = 0.981(2), z = 0.722(2) x = 0.733(2), z = 0.865(3) x = 0.342(2), z = 0.451(2) x = 0.505(3), z = 0.989(2) x = 0.642(2), z = 0.545(2)
x = 0.000a , z = 0.500a x = 0.892(1), z = 0.072(2) x = 0.131(1), z = 0.931(1) x = 0.706(4), z = 0.322(5) x = 0.684(4), z = 0.324(5) x = 0.585(2), z = 0.713(2) x = 0.349(2), z = 0.707(2) x = 0.299(3), z = 0.678(2) x = 0.011(3), z = 0.289(2) x = 0.273(3), z = 0.145(3) x = 0.985(3), z = 0.730(2) x = 0.751(3), z = 0.876(3) x = 0.352(2), z = 0.456(3) x = 0.509(2), z = 0.025(2) x = 0.642(2), z = 0.547(3)
a
Fixed.
L.D. Gulay, I.D. Olekseyuk / Journal of Alloys and Compounds 396 (2005) 233–239
237
Table 5 Interatomic distances (δ, nm) and coordination numbers (C.N.) of the atoms in the R3.33 CuPb1.5 Se7 (R = Ho, Er and Tm) compounds Atoms
δ (nm)
C.N.
Ho3.33 CuPb1.5 Se7
Er3.33 CuPb1.5 Se7
Tm3.33 CuPb1.5 Se7
Lu3.33 CuPb1.5 Se7
R1–2Se7 R1–1Se1 R1–1Se3 R1–2Se5
0.273 0.279 0.284 0.289
0.275 0.276 0.286 0.290
0.274 0.268 0.293 0.280
0.2798 0.2721 0.2868 0.2809
6
R2–2Se6 R2–1Se1 R2–2Se2 R2–1Se4
0.279(4) 0.284(5) 0.294(3) 0.295(4)
0.293(3) 0.282(3) 0.288(2) 0.288(4)
0.272(2) 0.279(4) 0.287(3) 0.270(4)
0.283(1) 0.2797(9) 0.2796(5) 0.2818(9)
6
R3–2Se4 R3–1Se3 R3–1Se2 R3–2Se6
0.274(3) 0.277(5) 0.278(4) 0.292(4)
0.276(2) 0.278(3) 0.281(4) 0.279(3)
0.278(3) 0.278(3) 0.288(4) 0.302(2)
0.2781(6) 0.278(1) 0.2766(8) 0.285(1)
6
M1–2Se5 M1–1Se7 M1–2Se1 M1–2Se2
0.304(4) 0.306(5) 0.307(5) 0.346(5)
0.305(4) 0.309(6) 0.307(5) 0.338(5)
0.303(5) 0.314(7) 0.326(5) 0.329(6)
0.2967(9) 0.303(1) 0.3281(9) 0.332(1)
7
M2–2Se1 M2–1Se7 M2–2Se5 M2–2Se2
0.289(4) 0.300(5) 0.320(4) 0.354(5)
0.299(4) 0.288(5) 0.304(4) 0.355(4)
0.304(5) 0.298(7) 0.318(5) 0.345(6)
0.2842(7) 0.300(1) 0.3387(9) 0.345(1)
7
Cu–1Se7 Cu–1Se4 Cu–2Se3
0.230(4) 0.232(4) 0.253(3)
0.241(4) 0.242(4) 0.248(2)
0.239(4) 0.263(5) 0.247(3)
0.249(1) 0.241(1) 0.2451(6)
4
Pb1–2Se3 Pb1–1Se5 Pb1–2Se4 Pb1–2Se7
0.295(4) 0.324(5) 0.330(4) 0.339(4)
0.273(3) 0.313(4) 0.348(3) 0.356(3)
0.270(3) 0.315(4) 0.342(4) 0.362(3)
0.2703(8) 0.304(1) 0.344(1) 0.3471(9)
7
Pb2–1Se5 Pb2–2Se3 Pb2–2Se7 Pb2–2Se4
0.294(4) 0.308(4) 0.313(3) 0.347(4)
0.312(4) 0.317(3) 0.310(3) 0.333(3)
0.303(5) 0.316(4) 0.309(4) 0.338(4)
0.299(1) 0.3149(9) 0.2994(8) 0.334(1)
7
Se1–1R1 Se1–1R2 Se1–2M2 Se1–2M1
0.279 0.284(5) 0.289(4) 0.307(5)
0.276 0.282(3) 0.299(4) 0.307(5)
0.268 0.279(4) 0.304(5) 0.326(5)
0.2721 0.2797(9) 0.2842(7) 0.3281(9)
6-2
Se2–1R3 Se2–2R2 Se2–2M1 Se2–2M2
0.278(4) 0.294(3) 0.346(5) 0.354(5)
0.281(4) 0.288(2) 0.338(5) 0.355(4)
0.288(4) 0.287(3) 0.329(6) 0.345(6)
0.2766(8) 0.2796(5) 0.332(1) 0.345(1)
7-2
Se3–2Cu Se3–1R3 Se3–1R1 Se3–2Pb1 Se3–2Pb2
0.253(3) 0.277(5) 0.284 0.295(4) 0.308(4)
0.248(2) 0.278(3) 0.286 0.273(3) 0.317(3)
0.247(3) 0.278(3) 0.293 0.270(3) 0.316(4)
0.2451(6) 0.278(1) 0.2868 0.2703(8) 0.3149(9)
8-2
Se4–1Cu Se4–2R3 Se4–1R2 Se4–2Pb1 Se4–2Pb2
0.232(4) 0.274(3) 0.295(4) 0.330(4) 0.347(4)
0.242(4) 0.276(2) 0.288(4) 0.348(3) 0.333(3)
0.263(5) 0.278(3) 0.270(4) 0.342(4) 0.338(4)
0.241(1) 0.2781(6) 0.2818(9) 0.344(1) 0.334(1)
8-2
Se5–2R1 Se5–1Pb2 Se5–2M1 Se5–2M2 Se5–1Pb1
0.289 0.294(4) 0.304(4) 0.320(4) 0.324(5)
0.290 0.312(4) 0.305(4) 0.304(4) 0.313(4)
0.280 0.303(5) 0.303(5) 0.318(5) 0.315(4)
0.2809 0.299(1) 0.2967(9) 0.3387(9) 0.304(1)
8-3
Se6–2R2
0.279(4)
0.293(3)
0.272(2)
0.283(1)
4
238
L.D. Gulay, I.D. Olekseyuk / Journal of Alloys and Compounds 396 (2005) 233–239
Table 5 (Continud ) Atoms
δ (nm) Ho3.33 CuPb1.5 Se7
Er3.33 CuPb1.5 Se7
Tm3.33 CuPb1.5 Se7
Lu3.33 CuPb1.5 Se7
Se6–2R3
0.292(4)
0.279(3)
0.302(2)
0.285(1)
Se7–1Cu Se7–2R1 Se7–1M2 Se7–1M1 Se7–2Pb2 Se7–2Pb1
0.230(4) 0.273 0.300(5) 0.306(5) 0.313(3) 0.339(4)
0.241(4) 0.275 0.288(5) 0.309(6) 0.310(3) 0.356(3)
0.239(4) 0.274 0.298(7) 0.314(7) 0.309(4) 0.362(3)
0.249(1) 0.2798 0.300(1) 0.303(1) 0.2994(8) 0.3471(9)
C.N.
trigonal prisms for M1 (M2) and Pb1 (Pb2). The atoms of the statistical mixtures M1 (M2) and the Pb1 (Pb2) atoms are slightly shifted from the centers of corresponding prisms. The M1 + M2- and Pb1 + Pb2-centered trigonal prisms as combination of the M1-, M2- and Pb1-, Pb2-centered trigonal prisms in the structure of the Lu3.33 CuPb1.5 Se7 compound are shown in Fig. 3. The crystal structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds can be derived from the structure of the binary Y5 Se7 compound [16]. The positions of the Y (R) atoms with octahedral coordination in the binary Y5 Se7 compound and quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds are similar. Every position of the Y atom with trigonal prismatic coordination in the Y5 Se7 compound corresponds to two defect positions of the atoms of the statistical mixture M (R + Pb) or Pb in the structures of the R3.33 CuPb1.5 Se7
9-3
Table 6 The relations between the crystal structures of the compounds Y5 Se7 and Lu3.33 CuPb1.5 Se7 Y5 Se7 Space group Cm a = 1.3213 nm b = 0.39490 nm c = 1.2035 nm β = 104.82◦ Y1 2(a) x 0 z; x = 0.000, z = 0.500 Y2 2(a) x 0 z; x = 0.6928, z = 0.3095 Y3 2(a) x 0 z; x = 0.8829, z = 0.0786 Y4 2(a) x 0 z; x = 0.1119, z = 0.9259 Y5 2(a) x 0 z; x = 0.3012, z = 0.6951 Se1 2(a) x 0 z; x = 0.0376, z = 0.2857 Se2 2(a) x 0 z; x = 0.2597, z = 0.1509 Se3 2(a) x 0 z; x = 0.9620, z = 0.7185 Se4 2(a) x 0 z; x = 0.7400, z = 0.8538 Se5 2(a) x 0 z; x = 0.3400, z = 0.4523 Se6 2(a) x 0 z; x = 0.5106, z = 0.0182 Se7 2(a) x 0 z; x = 0.6598, z = 0.5532
Lu3.33 CuPb1.5 Se7 Space group Cm a = 1.3404 nm b = 0.40307 nm c = 1.2475 nm β = 104.36◦ Lu1 2(a) x 0 z; x = 0.0000, z = 0.5000 M1 2(a) x 0 z; x = 0.7092, z = 0.3249 M2 2(a) x 0 z; x = 0.6635, z = 0.3076 Lu2 2(a) x 0 z; x = 0.8806, z = 0.0713 Lu3 2(a) x 0 z; x = 0.1196, z = 0.9313 Pb1 2(a) x 0 z; x = 0.3426, z = 0.7002 Pb2 2(a) x 0 z; x = 0.2944, z = 0.6765 Se1 2(a) x 0 z; x = 0.0102, z = 0.2849 Se2 2(a) x 0 z; x = 0.2620, z = 0.1341 Se3 2(a) x 0 z; x = 0.9807, z = 0.7239 Se4 2(a) x 0 z; x = 0.7344, z = 0.8654 Se5 2(a) x 0 z; x = 0.3493, z = 0.4581 Se6 2(a) x 0 z; x = 0.498, z = 0.000 Se7 2(a) x 0 z; x = 0.6494, z = 0.5444 Cu 2(a) x 0 z; x = 0.5821, z = 0.7141
(R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds. An additional position of the Cu atoms with tetrahedral coordination exists in the structures of the quaternary R3.33 CuPb1.5 Se7 (R = Tb, Dy, Ho, Er, Tm, Yb and Lu) compounds when compared with Y5 Se7 . The relation between the crystal structures of the compounds Y5 Se7 and Lu3.33 CuPb1.5 Se7 is described in Table 6.
Fig. 2. The unit cell and coordination polyhedra of the Lu1 (a), Lu2 (b), Lu3 (c), M1 (Lu + Pb) (d), M2 (Lu + Pb) (e), Cu (f), Pb1 (g), Pb2 (h), Se1 (i), Se2 (j), Se3 (k), Se4 (l), Se5 (m), Se6 (n), Se7 (o) atoms in the structure of the Lu3.33 CuPb1.5 Se7 compound.
Fig. 3. The M1 + M2- and Pb1 + Pb2-centered trigonal prisms as combination of the M1-, M2- and Pb1-, Pb2-centered trigonal prisms in the structure of the Lu3.33 CuPb1.5 Se7 compound.
L.D. Gulay, I.D. Olekseyuk / Journal of Alloys and Compounds 396 (2005) 233–239
Acknowledgement The authors are grateful to Prof. A. Pietraszko (W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wrocław, Poland) for the assistance in single crystal data collection.
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