INTERATOMIC FORCE-CONSTANTS FROM FIRST PRINCIPLES - THE CASE OF ALPHA-QUARTZ

We describe a method for calculating the interatomic force constants i n crystalline insulators, from first principles, with explicit inclusi on of the long-ranged anisotropic dipole-dipole interaction. Using thi s technique, the dynamics of alpha-quartz, a model for tetrahedrally b onded silica, is investigated: we examine the range of interatomic for ces, their anisotropy, their longitudinal and transverse character, an d the importance of the dipole-dipole contribution. These force consta nts provide an extensive database for testing semiempirical interatomi c potentials used in silica molecular-dynamics simulations.