First-Principles Forecast of Gapless Half-Metallic and Spin-Gapless Semiconducting Materials: Case Study of Inverse Ti2CoSi-Based Compounds

Abstract

First-principles calculations were used to investigate several inverse Ti2CoSi-based compounds. Our results indicate that Ti2CoSi could transform from a spin-gapless semiconductor to a half metal if a quarter of the Co atoms are replaced by Ti. Ti2.25Co0.75Si would keep stable half-metallic properties in a large range of lattice parameter under the effect of hydrostatic strain, and would become a gapless half metal under the effect of tetragonal distortion. Furthermore, we substituted B, Al, Ga, P, As, and Sb for Si in the Ti2.25Co0.75Si compound. Our results demonstrate that Ti2.25Co0.75Si0.5B0.5, Ti2.25Co0.75Si0.5Al0.5, and Ti2.25Co0.75Si0.5Ga0.5 are half-metallic ferromagnetic materials, and Ti2.25Co0.75Si0.5P0.5, Ti2.25Co0.75Si0.5As0.5, and Ti2.25Co0.75Si0.5Sb0.5 are spin-gapless semiconducting materials. The introduced impurity atoms may adjust the valence electron configuration, change the charge concentration, and shift the location of the Fermi level.