Crystal Dynamics of Rubidium. I. Measurements and Harmonic Analysis

Abstract

Dispersion curves for lattice vibrations propagating along the five major symmetry directions in a single crystal of rubidium have been measured using inelastic neutron scattering. Care has been taken to identify spurious peaks in the neutron groups and to correct for effects of instrumental resolution. The results, at 12, 85, 120, and 205 °K, have been analyzed within the harmonic framework to yield atomic force constants, which were used to compute the phonon frequency distribution and frequency contours in the (100) and [Formula: see text] planes. A reciprocal space analysis has also been performed. The results are compared with previous measurements on the lighter alkali metals, and with the calculations of Toya and of Price, Singwi, and Tosi.