Lattice dynamics of ionic molecular crystals in the rigid ion approximation, phases II and III of sodium superoxide

Abstract

Quasi-harmonic lattice dynamics is developed for ionic molecular crystals, within the framework of the rigid ion approximation. Long-range electrostatic potentials as well as short-range atom–atom interactions are discussed, making extensive use of the Ewald long wave method. A computer program based on this theory has been developed, and phonon calculations have been carried out for phases II and III of solid Na+O2−. The calculated quantities are then compared with experimental data.