Third-order elastic moduli for alkali-halide crystals possessing the sodium chloride structure

The values of third-order elastic moduli for alkali halides, having NaCl-type crystal structure are calculated according to the Born–Mayer potential model, considering the repulsive interactions up to the second nearest neighbours and calculating the values of the potential parameters for each crystal, independently, from the compressibility data. This work presents the first published account of the calculation of the third-order elastic moduli taking the actual value of the potential parameter unlike the earlier works. Third-order elastic constants have been computed for alkali halides at 0 and 300 K. The results of the third-order elastic constants are compared with the available experimental and theoretical data. Very good agreement between experimental and theoretical third-order elastic constant data (except C123) is found. We have also computed the values of the pressure derivatives of second-order elastic constants and Anderson–Grüneisen parameter for alkali halides, which agree reasonably well with the experimental values, indicating the satisfactory nature of our computed data for third-order elastic constants.