Photoelastic constants in diamond and silicon

Ab Initio calculations, using density functional theory within the AIMPRO code, have been performed on bulk diamond and silicon in order to calculate the change in the dielectric constant due to strain, and hence the values of the photoelastic tensors. A combination of compressive and tensile strain has been applied to two atom unit cells of Si and diamond and the tensors relating to p(11) + 2p(12), p(12) - 2p(11) and p(44) extracted. Good agreement is found with experimental results for absolute values and frequency dependence of the constants for silicon. Results are also given for diamond where experimental data is much more limited and scattered. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim