Coordination number for the Li⁺-F^- ion pair in water

A cluster of 200 molecules of water containing the Li+-F- ion pair has been studied using Monte Carlo techniques. Two temperatures (T=298 and 500°K) and three different distances for the Li+-F- separation [R(Li-F)=2.0, 6.0, and 10.0 Å] have been considered. The water-water potential is obtained from quantum-mechanical Hartree-Fock-type computations corrected by inclusion of dispersion forces; the ion-water potential has been obtained from Hartree-Fock computations for the Li +-F--H2O complex. The Monte Carlo simulation provides reproducible information on the cluster shape, on the cluster structure, and on the coordination numbers for the Li+ cation and the F- anion, when in presence of one another. Copyright © 1975 American Institute of Physics.