AB-INITIO CALCULATION OF STRUCTURAL, LATTICE DYNAMICAL, AND THERMAL-PROPERTIES OF CUBIC SILICON-CARBIDE

We present first-principles calculations of the structural, lattice dynamical, and thermal properties as well as Raman results for cubic silicon carbide (3C SIG). The plane-wave pseudopotential approach to density functional theory (DFT) in the local density approximation has been used to calculate the equilibrium properties of 3C SiC, i.e., the ground-state energy, the band structure, the valence electron density, the lattice constant, the bulk modulus, its pressure derivative, and the ionicity factor of the chemical bonds. The linear-response theory within DFT. has been used to obtain the phonon frequencies, the eigenvectors, and the mean-square atomic displacements. Furthermore, we calculated the mode Gruneisen parameters, the internal-strain parameter, the elastic constants, the Born effective charge, and the high-frequency dielectric constant. The specific heat at constant volume and at constant pressure, the thermal expansion coefficient, the temperature dependence of the lattice constant, and that of the isothermal and adiabatic bulk modulus have been derived within the quasi-harmonic approximation. Finally, the second-order Raman spectrum of 3C SIC has been calculated using phenomenological polarizability coefficients and ab initio frequencies and eigenvectors. (C) 1995 John Wiley & Sons, Inc.