THEORETICAL-STUDY OF STRUCTURAL AND LATTICE DYNAMICAL PROPERTIES OF MGF2 USING A PAIR-POTENTIAL MODEL

A two-body interatomic potential model for magnesium difluoride (MgF2) is constructed from the known crystal structure and elastic constants . The reliability of this potential model is critically evaluated thro ugh the calculation of structural and lattice dynamical properties of MgF2 in sellaite phase with rutile structure. Energy minimization tech niques have been used to predict the lattice parameters and structural properties of MgF2 both at ambient and elevated pressure conditions. It was found that the calculated structural properties are in excellen t agreement with the experimental results. Harmonic lattice dynamical calculations have been performed on the equilibriated structure corres ponding to the potential energy minimum. The computed phonon frequenci es are in good agreement with experimental data and phonon dispersion curves are reproduced just as well. Frequencies calculated throughout the Brillouin zone have been used to construct a frequency distributio n function and harmonic contribution to the specific heat is also calc ulated.