THEORETICAL-STUDY OF THE ELASTIC AND THERMODYNAMIC PROPERTIES OF SODIUM-CHLORIDE UNDER PRESSURE

We have calculated the pressure-volume relationship at 293 K, the pressure dependence of the elastic constants, and some other thermodynamic properties of sodium chloride, using two rigid-ion models. Monte Carlo simulations, anharmonic perturbation theory, and quasiharmonic theory were used as appropriate. Special care has been taken to make sure that the numerical results are of benchmark quality they accurately reflect the predictions of the models used. The results show the necessity of including a second-neighbor interaction between like ions. Without this interaction the B1-B2 phase transition occurs at much too low a pressure. We find good agreement with experiment at high pressures except for the deviation from the Cauchy relation. We use our results to extract quantitative predictions on the volume dependence of three-body forces in NaCl. © 1990 The American Physical Society.