35 research outputs found
Second harmonic generation in SiC polytypes
LMTO calculations are presented for the frequency dependent second harmonic
generation (SHG) in the polytypes 2H, 4H, 6H, 15R and 3C of SiC. All
independent tensor components are calculated. The spectral features and the
ratios of the 333 to 311 tensorial components are studied as a function of the
degree of hexagonality. The relationship to the linear optical response and the
underlying band structure are investigated. SHG is suggested to be a sensitive
tool for investigating the near band edge interband excitations.Comment: 12 pages, 10 figure
Implementation of an all-electron GW approximation based on the PAW method without plasmon pole approximation: application to Si, SiC, AlAs, InAs, NaH and KH
A new implementation of the GW approximation (GWA) based on the all-electron
Projector-Augmented-Wave method (PAW) is presented, where the screened Coulomb
interaction is computed within the Random Phase Approximation (RPA) instead of
the plasmon-pole model. Two different ways of computing the self-energy are
reported. The method is used successfully to determine the quasiparticle
energies of six semiconducting or insulating materials: Si, SiC, AlAs, InAs,
NaH and KH. To illustrate the novelty of the method the real and imaginary part
of the frequency-dependent self-energy together with the spectral function of
silicon are computed. Finally, the GWA results are compared with other
calculations, highlighting that all-electron GWA results can differ markedly
from those based on pseudopotential approaches.Comment: 11pages,3figures, submitted to PR