Calculation of optical properties of white tin

Abstract

A calculation of the imaginary part of the interband dielectric constant is presented. Transition matrix elements have been obtained using a full OPW expansion of the crystal wavefunctions. It was found that core contributions to the matrix elements cannot be neglected in general, although the plane wave part of the wavefunction determines largely the value of the matrix elements. It is shown that all structures in the omega ² epsilon ₂ spectra originate from critical point absorption NFE regions in the Brillouin zone do not contribute much to the spectra. It is indicated that a k independent and band-pair dependent transition matrix element approximation can be very appropriate in interpreting optical spectra.