POTENTIAL-ENERGY FUNCTIONS FOR ATOMIC SOLIDS .3. FITTING PHONON FREQUENCIES AND ELASTIC-CONSTANTS OF DIAMOND STRUCTURES

Potential functions have been derived for the bulk phases of C, Si and Ge which reproduce the lattice energies, lattice spacings, elastic constants and the main features of the phonon dispersion curves of the diamond structures. These potentials all make the diamond lattice more stable than the simple cubic, body-centred cubic and face-centred cubic structures; for Si and Ge this is the order or decreasing stability. The potentials have a form suitable for use in studies of melting, defect structures, surface properties, etc.