Calculation of the molecular rotational potential from Bragg scattering data: the method and an application to (NH₄)₂SnCl₆

Abstract

The distribution of orientationally disordered rigid molecules is governed by the rotational potential. The authors present a procedure by which they derive the rotational potential from Bragg scattering. The analysis is applied to neutron diffraction data from (NH4)2SnCl6 taken at T=293 and 140K, respectively. The new method gives a better fit to the data than the conventional crystal structure analysis. The computed rotational potential is temperature-independent at least between room temperature and 140K, and the rotational barriers are consistent with the observed activation energy.