Lattice dynamics and thermal crystallographic parameters in phenothiazine

A computer program has been developed to study the lattice dynamics of molecular crystals in the harmonic approximation with the external Born-von Kármán formalism and an atom-atom potential function. Dispersion curves are obtained for monoclinic phenothiazine together with frequency distribution functions and external mode contribution to thermodynamic functions. Lattice dynamical T, L and S rigid-body tensors are obtained and individual thermal tensors are compared with experiment. The disagreement with respect to experimental results is of the same order as the disagreement with a Schomaker-Trueblood fit of experimental data.