Molecular motions in solid isotopic silanes

Abstract

This paper reports the results of measurements of some thermodynamic properties (heat capacities, vapour pressures, density, heats of fusion) of two silanes, SiH₄ and SiHD₃, over a wide temperature range above T= 2.8 K. Residual entropies (neglecting nuclear spins) have been computed to be –0.3 ± 0.3 cal mol^–1 deg.^–1 for SiH₄ and 2.5 ± 0.3 cal mol^–1 deg.^–1 for SiHD₃. These results together with published ones from other kinds of experiments are compared with the more extensive data that are available for the solid isotopic methanes. The similarities and differences are used for making deductions about molecular motions in the solid silanes.