First-principles band-structure calculation of yttrium oxysulfide

The electronic structure of yttrium oxysulfide (Y2O2S) is investigated using first-principles pseudopotential calculations by means of the local-density approximation within density-functional theory. It is found that ii) the material is an indirect band-gap semiconductor, (ii) the calculated bulk modulus (142 GPa) is between the one of yttrium oxide and that of yttrium sulfide, (iii) the top of the valence bands shows anisotropic behavior, and (iv) substantial covalent bonds between Y and O and less covalent bonds between Y and S coexist in the material. [S0163-1829(98)01016-9].