Hybrid-Functional and Quasi-Particle Calculations of Band Structures of Mg2Si, Mg2Ge, and Mg2Sn

摘要: We perform hybrid functional and quasi-particle band structure calculations with spin-orbit interaction to investigate the structures of Mg2Si, Mg2Ge, Mg2Sn. For all Mg2X materials, where X = Si, Ge, Sn, characteristics edge states, i.e., valley degeneracies, orbital characters, are found be conserved, independent computational schemes such as density generalized gradient approximation, functionals, or calculations. However, magnitude calculated gap varies significantly schemes. Within density-functional calculations, one-particle gaps Mg2Sn 0.191, 0.090, -0.346 eV, respectively, thus severely underestimated compared experimental gaps, due error in theory significant relativistic effect on low-energy structures. By employing hybrid-functional a 35% fraction exact Hartree-Fock exchange energy (HSE-35%), we overcame negative issue Finally, top HSE-35% Hamiltonians, obtained 0.835, 0.759, 0.244 eV for Mg2Sn, consistent 0.77, 0.74, 0.36 respectively.