Anion coordination geometry as a determining factor in crystallographic shear

Abstract

ATTENTION has been drawn to some of the consequences of anion polarisation in one crystallographic shear (CS) system, the reduced titanium oxides1; particularly to the effect on crystal energy and cation coordination geometry. The existence of polarisation in typical CS structures is indicated by the values of certain common properties—the dielectric constant and refractive index are both high—by the more direct, experimental determination of net ion charges in some double CS (column, or so-called ‘block’) structures2, and by the characteristic persistence of the cation coordination geometry3, which is invariably octahedral.