On the structural dynamics of plastically crystalline alkali hydroxides

Abstract
In their high-temperature cubic phase the alkali hydroxides NaOH and KOH and the corresponding deuterated compounds are described by an elastic dipole model for the reorienting OH- groups. The theory describes thermo-diffuse scattering, Huang scattering and phonon softening. The inelastic data and the dispersions of the acoustic modes of KOD are shown and interpreted. Similarities to cooperative Jahn-Teller compounds and alkali cyanides are discussed.