Refinement of the structure of ζ-Nb2O5and its relationship to the rutile and thoreaulite structures

摘要

The crystal structure of ζ-Nb2O5, space groupC2/c, a12.740(2),b4.8830(6),c5.5609(6)Å,β105.02(1)°, Z 4, has been refined toR1.6 for 457 observed reflections (MoKα). The coordination polyhedron of the niobium atom is a distorted octahedron; the crystal structure consists of two-octahedron-thick, rutile-like layers separated by crystallographic shear (CS) planes. Relative to the rutile structure, these planes are indexed (101) and adjacent layers are related by the CS vector. Members of the thoreaulite-foordite series have topologically identical two-octahedron-thick (101) sheets; however, here the CS vectorr, coupled with the translation vectorrresults in the insertion of a plane of square antiprism interstices between adjacent octahedral sh