Generalized Grüneisen Parameters in the Anisotropic Debye Model

The description of anharmonic effects in solids involves generalized Gr\"uneisen parameters which measure the strain dependence of the lattice vibrational frequencies. These parameters are here expressed in the Debye approximation in terms of second- and third-order elastic coefficients for arbitrary crystal symmetry. The general relations are also specialized to cubic point groups with a fourfold axis.