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Abstract: First-principles and pseudopotential approaches have been used to investigate band structures and pressure dependence of the bandgaps of zincblende Ge50Sn50 ordered alloy up to 9 GPa. It is found that the direct bandgap increases almost linearly with pressure to a maximum value 0.72 eV at 4.7 GPa where direct-to-indirect at L point transition of the bandgap takes place. At 6.8 GPa, an indirect bandgap transition from L to Δ 1 (near X) point takes place. [Copyright &y& Elsevier]

Abstract: First principles and pseudopotential approaches have been used to investigate the electronic properties of α and β polymorphs about compounds Ti3SiC2 and Ti3GeC2. In order to study the variations in properties induced by two different elements in the same phase, the effects of Si substitution to Ge are considered. For both α and β-phase, it is found that the replacement of Ge to Si doesn'' t change much their original electronic properties, and the main differences in total density of states between −9 to −6 eV mainly derive from the changes of s orbit at 2b or 2d Wyckoff positions. [Copyright &y& Elsevier]