No abstract

Within the context of the quasiharmonic theory of lattice dynamics, the zone center frequencies, dispersion curves, and frequency distribution of sodium azide are calculated using two potential models. Good agreement is obtained between the calculated zone center frequencies and the available Raman data. In particular, the calculated temperature dependence of the splitting of the Eg librational mode in the β phase into Ag and Bg modes in the α phase is in excellent agreement with experiment.

The self-consistent phonon approximation is applied to small crystallites of N argon atoms, in the range 3 & N & 15. The temperature dependence of the lattice constant, frequencies, internal energy, free energy, specific heat, and entropy, for each cluster size, is reported. The variation of these quantities with N is also given. The equilibrium structures are quantum mechanically determined at each temperature and are found to agree with classical results. Comparisons with normal-mode calculations and with bulk behavior are given.

No abstract

No abstract