The incommensurate composite YₓOs₄B₄ (x = 1.161)

Abstract

YₓOs₄B₄ (x = 1.161) crystallizes as a tetragonal incommensurate composite of columns of Y atoms extending along [001] in an Os₄B₄ framework. The structure was refined using the superspace approach. The basic structure of the Y subsystem can be idealized as having I4/mmm symmetry, with a crystallographically unique Y atom located on the 4/mmm position. The actual superspace symmetry is P4₂/nmc(00σ₃)s0s0. The Y atoms feature only subtle positional modulation in the [001] direction. The Os₄B₄ subsystem [P4₂/ncm(00σ₃)00ss superspace symmetry] is built of columns of edge-sharing Os₄ tetrahedra extending along [001] and B₂ dumbbells. The Os₄ tetrahedra feature pronounced positional modulation with a distinct variation of the Os-Os bond lengths. Modulation of the B₂ dumbbells is best described as a rotation about the [001] axis.