Rigid-ion models of the interionic potential in the alkali halides

Monte Carlo calculations have been made on the basis of the rigid-ion model for a number of alkali halides at zero applied pressure in the solid state at 298K and both solid and liquid phases near the melting temperatures. Two different forms of the short-range repulsive interaction were used: an exponential potential of the Huggins-Mayer form (1933) and an inverse-power repulsive potential in the form due to Pauling (1928). The potential parameters were in all cases taken from the work of Tosi and Fumi (1964). Some care has been taken to minimize errors in the calculation of the coulombic energy and the accuracy of the results is believed to be considerably greater than that previously achieved in the computer simulation of ionic systems. The Huggins-Mayer form of the potential is found to be superior to the Pauling form in virtually all respects.