In:
Zeitschrift für Naturforschung B, Walter de Gruyter GmbH, Vol. 59, No. 2 ( 2004-2-1), p. 174-181
Abstract:
Ternary silicides RE 2 RE′ 3 Si 4 (RE = La, Ce; RE′= Y, Lu) were synthesized by arc-melting of the elements. Single crystals were grown by annealing the arc-molten buttons slightly below the melting points in water-cooled silica tubes in an induction furnace. Five silicides RE 2 RE 3 ′Si 4 were investigated by X-ray powder and single crystal diffraction: Zr 5 Si 4 type, P4 1 2 1 2, a = 779.4(3), c = 1441.3(9) pm, wR2 = 0.072, 1806 F 2 values, 45 variables for La 1.72(4) Y 3.28(4) Si 4 , P4 3 2 1 2, a = 769.92(7), c = 1412.3(1) pm, wR2 = 0.079, 1846 F 2 values, 45 variables, BASF = 0.36(4) for La 1.72(2) Lu 3.28(2) Si 4 , P4 1 2 1 2, a = 778.6(1), c = 1433.9(3) pm, wR2 = 0.054, 1910 F 2 values, 46 variables, BASF = 0.34(4) for Ce 1.82(6) Lu 3.18(6) Si 4 , P4 3 2 1 2, a = 778.8(3), c = 1436.0(10) pm, wR2 = 0.166, 1916 F 2 values, 45 variables for Ce 1.71(7) Y 3.29(7) Si 4 , and Sm 5 Ge 4 type, Pnma, a = 749.2(2), b = 1484.2(7), c = 780.3(2) pm, wR2 = 0.070, 1956 F 2 values and 49 variables for Ce 1.47(3) Y 3.53(3) Si 4 . The local coordinations of both structure types are very similar, i. e. CN 18, 16, and 14 coordination polyhedra for the RE1, RE2, and RE3 atoms. The main structural motif is the eightfold coordination of the RE3 positions by rare earth metal atoms. These slightly distorted RERE’ 8 cubes are condensed via common corners (Zr 5 Si 4 type) or via common edges (Sm 5 Ge 4 type). All silicon atoms in these silicides form Si 2 pairs at Si-Si distances ranging from 254 to 258 pm. DFT band structure calculations confirm the metallic character of both silicides and the trivalent state of cerium in Ce 5 Si 4 . The COHP analysis (Crystal Orbital Hamilton Population) of the Si-Si bonds shows a significant occupation of Si-Si antibonding orbitals, which is partially compensated by a Si-Si π*,σ*Y-4d (Ce-5d) back donation.
Type of Medium:
Online Resource
ISSN:
1865-7117
,
0932-0776
DOI:
10.1515/znb-2004-0209
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
2004
detail.hit.zdb_id:
2078109-X
detail.hit.zdb_id:
124635-5
