Abstract:
We have employed the ab initio plane-wave pseudopotential method, within a local-density approximation of the density-functional theory, and a linear-response approach, to investigate structural, electronic and phonon properties of boron compounds (BP, BAs, and BSb). The calculated structural and electronic results for these semiconductors are in good agreement with available theoretical and experimental studies. In addition to these bulk studies, the elastic constants of zinc-blende boron compounds and beryllium chalcogenides have been calculated using the volume-conserving tetragonal and monoclinic strains. In particular, a good agreement has been observed between our calculated elastic constants and their experimental values for BP semiconductor. Furthermore, we have made theoretical investigations of the atomic geometry, electronic structure, and lattice dynamics of the (110) surface of boron compounds and beryllium chalcogenides. The structural properties for these surfaces are compared with previous structural results obtained for other III-V(110) and II-VI(110) surfaces in detail. Our results clearly indicate that the electronic structure for these surfaces is semiconductor due to separation between a highest occupied surface state and lowest unoccupied surface state. The origins of various phonon modes on these surfaces are discussed and their variations for different compounds are analyzed in terms of the reduced mass and total mass differences. Moreover, surface phonon modes on these surfaces are compared with the corresponding phonon modes on other III-V(110) and II-VI(110) surfaces. From this comparison, some differences are observed and they are explained according to mass differences and ionicity factor.
