On the evaluation of the van der Waals potentials in ionic crystals

Abstract

An application of the Slater–Kirkwood variational method has been made to evaluate the van der Waals dipole–dipole and dipole–quadrupole energies in the four families of ionic crystals, viz., alkali halides, alkaline earth chalcogenides, alkali chalcogenides, and alkaline earth halides. The methods based on the perturbation theory adopted by previous investigators to evaluate the van der Waals potentials are critically discussed. In the present paper we have used an interpolation scheme and semiempirical formulas to estimate the dipole–dipole and the dipole–quadrupole coefficients between a number of different ions with electron configurations close to those of the rare gas atoms. An independent check of the approximate validity of the interpolation scheme has been provided by evaluating the dipole–dipole interaction coefficients between alkali metal atoms. The crystal energies of alkali halides, calculated using the new values of van der Waals potentials, agree closely with the experimental values.

Preferential Growth of α'-FeN Films under a High Magnetic Field

“…This set is now known [31] both to contain severe inconsistencies and to predict values that cannot stand comparison with modern ab initio computations [32][33][34][35]. Furthermore the potentials [28,29] contain semi-empirically determined dispersion coefficients [36] similar to those [37,38] now known [35] to be too large by factors of around three. These potentials do not, therefore, provide an attractive basis for investigating the structures of the encapsulated iodide nanocrystals.…”

Random pseudobinary ionic alloys: lattice energy and structural properties

“…However, we have also considered the possibility of refining the model including NNN repulsion [17] and Van der Waals [18] and three-body [19] interactions. We studied the effect of each term separately, considering the SQS configuration in the 16-atom FCC cell.…”

Analysis of the equation of state of lithium and sodium halides

“…The van der W a d s dipole-dipole and dipole-quadrupole potentials derived from the variational method [8] are used in the present calculations. Although there have been several attempts to study the ES of a few alkali halides [l, 91, no such comprehensive effort seems to have been made to treat all the halides of Li and Na a t a single place using a large number of different potential functions as in the present paper.…”

“…Values of X will be different for different potential forms of short-range repulsive energy whereas Y does not depend on the form of the repulsive potential. The repulsive potential parameters are calculated following the method suggested in 171 and the van der Waals constants C and D from [8].…”