PRECISE STRUCTURE-ANALYSIS BY NEUTRON-DIFFRACTION FOR RNBO4 AND DISTORTION OF NBO4 TETRAHEDRA

被引：75

作者：

TSUNEKAWA, S ^{[1
]}

KAMIYAMA, T ^{[1
]}

SASAKI, K ^{[1
]}

ASANO, H ^{[1
]}

FUKUDA, T ^{[1
]}

机构：

[1] UNIV TSUKUBA,INST MAT SCI,TSUKUBA 305,JAPAN

来源：

ACTA CRYSTALLOGRAPHICA SECTION A | 1993年 / 49卷

关键词：

D O I：

10.1107/S0108767392013035

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

Precise crystal structure analysis by neutron powder diffraction is performed for rare-earth orthoniobates (RNbO4: R = La, Nd, Ho and Yb) and the distortion of NbO4 tetrahedra is estimated with the normal-coordinate method. Displacement of the cubic symmetry mode is large and increases with decreasing ionic radius of (VIII)R3+. This displacement produces a regular tetrahedron of NbO4. The mean value of Nb-O distances in the regular tetrahedron of RNbO4 crystals is 1.834 angstrom. This value is nearly equal to the mean bond length for s = 5/4, RBAR = 1.828 angstrom, estimated by the bond-valence method. Displacements of the other symmetry modes slightly decrease or are almost constant with decreasing ionic radius.

引用

页码：595 / 600

页数：6

共 17 条

[1] CELL VOLUMES OF APO4, AVO4, AND ANBO4 COMPOUNDS, WHERE A = SC, Y, LA-LU [J].