Infrared Lattice Absorption of Silicon and Germanium

Abstract

Abstract The two‐phonon absorption bands of silicon and germanium are calculated taking into account the second‐order dipole moment up to second‐nearest neighbours. The agreement between the calculated and measured bands shows that the shell model used in our calculations gives quite good phonon dispersion curves. The detailed analysis of the remaining deviations between measured and calculated frequencies indicates that in some points of the Brillouin zone the shell model should be corrected.