CALCULATED STATIC AND DYNAMIC PROPERTIES OF BETA-SN AND SN-O COMPOUNDS

The static and dynamic properties of beta-Sn, SnO, and SnO2 are studie d using the full-potential linear-muffin-tin-orbital method within the local-density approximation (LDA). Equilibrium lattice parameters and bulk moduli (including pressure variations) are in excellent agreemen t with experimental values. The cohesive energies are calculated too l arge, in accordance with the usual overbinding found in the LDA. Optic al GAMMA-point phonon frequencies are obtained using the frozen phonon approach. For those phonon modes which have been measured, experiment al identifications are confirmed, with the single exception of the B1g mode of SnO, for which we find a frequency that is three times larger than the measured value. It is argued that the assignment of the obse rved mode is wrong.