Theoretical studies of SiC, AlN and their (110) surfaces

摘要

We have made theoretical investigations of the structural, elastic and lattice dynamical properties for zinc-blende SiC and AlN. The ground-state properties, i.e., the lattice constants, the bulk modulus, the first-order pressure derivative of the bulk modulus, and the elastic constants are calculated using a plane-wave pseudopotential method within the density-functional theory. A linear response approach based on density functional perturbation theory has been used to obtain phonon dispersion curves and density of states for these bulk materials. In particular, the calculated phonon spectrum for SiC is in good agreement with experimental data. We have also presented the structural properties of the (110) surface of these materials. Our calculated relaxed atomic geometries for both surfaces have been compared with previous theoretical calculations. Our structural parameters are further used to investigate the phonon-dispersion curves and the density of states for the SiC(110) and AlN(110) surfaces. We have found that the surface phonon modes on the SiC( 110) and AlN( 110) surfaces exhibit nearly similar displacement patterns. This is mainly due to the fact that both bulk materials have nearly identical lattice constants, as well as, a similar cation and anion mass difference.