An accurate, fully automated, theoretical ab initio scheme is presented for the calculation of elasto-optic constants of crystalline systems of any space group of symmetry. The approach is developed within periodic boundary conditions, exploits both translational and point symmetry, and allows for the use of several one-electron Hamiltonians, such as Hartree-Fock, Kohn-Sham, or hybrids. Generalized-gradient functionals are found to improve the agreement with experiments by a factor of 2 with respect to simple local-density ones, commonly used in the literature so far. The explicit dependence of elasto-optic constants from the electric field frequency can be evaluated as well, thus allowing for a closer comparison with experimental data that usually refer to finite frequencies. The relatively large uncertainty associated with experimental measurements, and the use of an electric field with finite wavelength, make the availability of a predictive theoretical scheme particularly helpful in interpreting the photoelastic response of crystals. The proposed scheme, which has been implemented in the crystal program, proves numerically stable with regard to its computational parameters and accurate with respect to elasto-optic constants of a set of eight crystals for which consolidated experimental values have been reported.

• Received 24 May 2013

DOI:https://doi.org/10.1103/PhysRevB.88.045121