Anharmonic calculations of the optical-phonon lifetime for crystals with the diamond structure

Anharmonic calculations of crystals having the diamond structure; silicon, germanium, diamond, and alpha-tin are reported. The principal channels of decay of the optical phonon are determined for each material. In particular the zone-center phonon lifetime is computed with the exception of alpha-tin. A reasonable agreement between theory and experiment is obtained considering the simplicity of the harmonic and anharmonic models employed in the present calculation. The linewidth of the optical phonon at a temperature of 10 K is found to be 1.19 cm^-1 for silicon, 0.53 cm^-1 for germanium, and 0.84 cm^-1 for diamond the experimental values being 1.24, 0.75, and 1.68 cm^-1, respectively. {} 1996 The American Physical Society.