Structure and some physicochemical properties of carbon and silicon phases with a LA3 diamond-like lattice

The structures and properties of two diamond-like C-LA3 and Si-LA3 phases with crystallographically equivalent atomic sites are calculated by density functional theory with the exchange-correlation potential in the generalized gradient approximation (DFT-GGA). For these phases the structural characteristics, cohesion energies, densities of states, and bulk moduli are determined and powder diffraction patterns are calculated. It is found that the cohesion energies, band gaps, and bulk moduli of C-LA3 and Si-LA3 phases are smaller than the corresponding values of cubic diamond and silicon. Possible methods to obtain experimentally diamond-like C-LA3 and Si-LA3 phases are also analyzed in the paper.