NEUTRON SPECTROSCOPY OF ALUMINUM TRIHYDRIDE

The lattice dynamics of alpha-AlH3 and alpha-AlD3 were studied by inel astic neutron scattering (INS). The hydrogen optic modes in the INS sp ectra were shown to form a broad structured band which exhibited an ha rmonic isotopic behaviour. In contrast, the low-energy part of the pho non spectra, formed mainly by the vibrations of the metal atoms, showe d pronounced anharmonicity. The temperature dependence of the AlH3 hea t capacity derived from the MS data agrees with the available experime ntal dependence at 50-150 K.