Ternary Hydrides Possessing the Cubic Perovskite Structure. II. Vibration Spectra by the Inelastic Scattering of Cold Neutrons

Abstract

Inelastic neutron scattering techniques in recent years have been employed in the study of lattice dynamics in solids. These techniques are particularly suited for the study of hydrogen-containing compounds because of the large incoherent scattering cross section of hydrogen and the absence of selection rules. In the present experiments we have obtained the vibration spectra of BaLiH3 and SrLiH3 by the energy-gain scattering of cold neutrons. Both these compounds have previously been shown to have the perovskite structure. The observed neutron time-of-flight spectra have been used to calculate approximate frequency distributions for each compound. Peak frequencies in cm−1 are: SrLiH3, 1130, 950, 660, and 340; BaLiH3, 920, 780, 650, and 320. These frequencies have been assigned in order of decreasing values to the Li–H stretch, the Li–H F2u bending mode, the Li–H F1u bending mode, and Sr–(LiH3) or Ba–(LiH3) stretch. Infrared data have also been obtained for both compounds as well as for the isostructural EuLiH3.