Mean-square ionic displacements and force constant of crystals with the CsCl type structure

Abstract Mean‐square vibrational amplitudes of ions in the diatomic lattices of crystals with the CsCl type structure have recently been determined in the high temperature region by elastic scattering of neutrons. An evaluation of mean‐square displacements in terms of frequency moments is derived and connections with the force constants of the crystals are worked out. The difference of the vibrational amplitudes of the two ions is calculated from the experimental data and by means of force constants derived from phonon measurements.