No abstract

We have carried out a first-principles total-energy calculation of the structural and the elastic properties for the series of boron compounds BP, BAs, and BSb. We have applied the augmented plane-wave plus local-orbitals method with both the local-density approximation (LDA) and the generalized gradient approximation (GGA). Since there have been no previous theoretical or experimental determinations, our calculations provide the first available information on the elastic constants of these materials. The elastic constants have been derived by the stress-strain relation. We have calculated all of the equilibrium structural parameters for both phases: rock salt and zinc blende structures.

In this work, we have investigated the structural, electronic and optical properties of the ternary I -III -VI 2 chalcopyrite semiconductors ABX 2 (A = Cu, B = In, Ga, X = Se) by means of a first-principles densityfunctional total-energy calculation with the local-density approximation (LDA), using the all-electron full-potential linear-augmented plane-wave method (FP-LAPW). The equilibrium lattice constants and the bulk moduli (a, c, c/a, u and B 0 ) are compared with other theoretical calculations. The energy gap at ambient pressure is found to be direct and the nature of the gap crucially depends on the manner in which the d electrons of the A atoms are treated. We have also reported the optical properties of two chalcopyrite semiconductors CuInSe 2 and CuGaSe 2 . Results on complex dielectric functions, refractive indices n, extinction coefficients k, and normal-incidence reflectivity R in the two crystals are given and compared with earlier data where available. We analyze in detail the structures of the dielectric function observed in the studied energy region.

No abstract

No abstract