STRUCTURAL, BONDING, AND ELECTRONIC-PROPERTIES OF IIA-IV ANTIFLUORITE COMPOUNDS

We have studied the electronic and structural properties of the antifluorite compounds Mg2X (X= Si, Ge, Sn), Be2C, and hypothetical compounds Mg2C and Be2Si using the first-principles pseudopotential total energy method. Five of the compounds are small-gap semiconductors, while Be2Si is a metal. Calculated lattice constants agree well with experiment for the four known compounds, but are consistently a few percent smaller than the reported values. The bulk moduli of this group of materials follow a semiempirical formula for B0 to within approximately 5%. Bulk moduli calculated from first principles, corrected for the underestimation of the lattice constant, agree well with the available experimental values.