Ab-Initio Prediction of Intrinsic Half-Metallicity in Binary Alkali-Metal Chalcogenides: KX (X = S, Se and Te)

First-principles full-potential linearized augmented plane-wave method based on density functional theory is used to investigate the structural, electronic and magnetic properties of KX (X = S, Se and Te) binary alkali-metal chalcogenides compounds. These compounds in different crystalline phases, NaCl (B1), CsCl (B2), ZB (B3), NiAs (B8(1)), WZ (B4) and Pnma, were calculated within the generalized gradient approximation (GGA-PBE) and the modified Becke-Johnson approach (mBJ-GGA-PBE) for the exchange-correlation energy and potential. We found that the most stable phase for the KX binary compounds is the nonmagnetic Pnma phase. The calculated lattice parameters, bulk moduli, their first-pressure derivatives and internal parameters are in good agreement with the other theoretical data. The electronic band structure and density of states show that half-metallic and magnetic character arises, which can be attributed to the presence of spin-polarized p orbitals in the group VI elements. KX (X = S, Se and Te) compounds, except for KSe and KTe in the CsCl and NiAs phases, show HM character in all phases, with an integer magnetic moment of 1 mu(B) per formula unit and HM gaps.