Pressure dependences of band gaps and optical-phonon frequency in cubic SiC

The high-pressure behavior of the direct and indirect band gaps in zinc-blende-structure SiC is examined with use of self-consistent ab initio pseudopotential calculations. The fundamental band gap from ${\mathrm{\Gamma }}_{15}^{\mathit{v}}$ to ${\mathit{X}}_1^{\mathit{c}}$ is found to decrease linearly with pressure up to 200 kbar. This result disagrees with a recent experimental finding of strong sublinear behavior at pressures of 10 to 15 kbar. The linear pressure coefficients of the fundamental band gap and the transverse-optical-phonon frequency at the Γ point in the Brillouin zone are in good agreement with measured values.