Calculated static and dynamic properties of β-Sn and Sn-O compounds

The static and dynamic properties of \ensuremath{\beta}-Sn, SnO, and ${\mathrm{SnO}}_{2}$ are studied 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 agreement with experimental values. The cohesive energies are calculated too large, in accordance with the usual overbinding found in the LDA. Optical \ensuremath{\Gamma}-point phonon frequencies are obtained using the frozen phonon approach. For those phonon modes which have been measured, experimental identifications are confirmed, with the single exception of the ${\mathit{B}}_{1\mathit{g}}$ 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 observed mode is wrong.