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We present the results of a first principles study on the ordered Ge[sub 0.50]C[sub 0.50] and Sn[sub 0.50]C[sub 0.50] cubic alloys. A linear combination of atomic orbitals approach in the framework of density functional theory is employed for total energy calculations in the zincblende phase. A fitting of the energy surface to the equation of state yields the lattice constant of 4.61 and 5.17 Å and the bulk modulus of 181 and 119 GPa for GeC and SnC, respectively. Analysis of band structure suggests a crossover of the nature of the band gap from indirect to direct in going from SiC to GeC to SnC. Although both alloys predicted to be unstable with respect to their elemental components at zero pressure and temperature, GeC appears to become stable at higher pressure. It appears that both the lattice constant and bulk modulus of the ordered alloys do not follow Végard's linear rule, though the calculated dielectric constant of the cubic alloys is approximately the average of the dielectric constant of their elemental components. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Studies the structural, electronic, and optical properties of the ordered Ge[sub 0.50]Sn[sub 0.50] alloy in the zinc-blende phase along with its stability with respect to the elemental components. Electron density functional theory calculations; Linear combination of atomic orbitals approach; Bloch functions.