Inelastic neutron scattering by the quasi two-dimensional librational modes in K2SnCl6

The origin of the diffuse streaks observed in the high temperature phase of K2SnCl6 is explained in terms of a dynamical model in which [SnCl6] octahedra are coupled by torsional springs. The magnitude and the temperature dependence of the torsional spring constants is derived from inelastic neutron scattering data. The librational modes are soft and overdamped at room temperature, and a central component is observed up to 170 K above the lattice instability which occurs at Tsub(c)1 = 261.5 K. (orig.)