Full ab initio calculation of second-order infrared and Raman spectra of elemental semiconductors

Abstract

Results of the first full ab initio calculation of the second-order infrared spectrum of silicon and of the second-order off-resonance Raman spectra of diamond, silicon, and germanium are presented. The lattice-dynamical quantities, the effective charge, and the electronic susceptibility are calculated by the density-functional perturbation theory within the LDA. A finite-difference method is used to obtain the non-linear dipole moment as the derivative of the effective charge and the first- and second-order derivatives of the susceptibility.