Approximate exchange and electrostatic interaction energies of deformed ions

Abstract

AbstractComputation of exchange‐polarization and electrostatic‐polarization interaction energies between ions is the most expensive step in ab initio investigations of the properties of perfect and imperfect ionic crystals. In the present paper approximate formulas are proposed for these quantities. They save about 95% of the computation time and give these values with an error less than 0.2 kcal mol−1 as compared to ab initio results. The formulas for the exchange‐ and electrostatic‐polarization energies involve the generalized overlap integral between the one‐determinantal wave functions of the deformed ions. The approximations are tested in the calculations of the interactions of deformed ions in LiF and NaF crystals.