ANHARMONIC CALCULATIONS OF THE OPTICAL-PHONON LIFETIME FOR CRYSTALS WITH THE DIAMOND STRUCTURE

Anharmonic calculations of crystals having the diamond structure; sili con, germanium, diamond, and alpha-tin are reported. The principal cha nnels of decay of the optical phonon are determined for each material. In particular the zone-center phonon lifetime is computed with the ex ception of alpha-tin. A reasonable agreement between theory and experi ment is obtained considering the simplicity of the harmonic and anharm onic 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 e xperimental values being 1.24, 0.75, and 1.68 cm(-1), respectively.