Infrared and Raman spectra and normal coordinate calculations on trirutile-type compounds

Abstract

The Raman and i.r.-spectra of trirutiles AB 2O 6 with A = Mg, Zn, Ni, Co and B = Sb, Ta and A′ 2TeO 6 with A′ = Al, Ga, Cr, Mn, Fe have been recorded on powder samples. For the trirutile-type structure Cartesian symmetry coordinates are given. Based on these coordinates a normal coordinate and force constant calculation has been performed. The TeO stretching force constant has a value of 3.1 mydn Å −1 which corresponds to the value predicted for a covalent single bond. The normal modes are discussed in relation to the potential energy distribution and to the vibrations of a free octahedron. Correlation splitting for the Raman-active octahedral vibrations of species A 1 g and B 2 g is computed to be very small.