A refined ionic model for clusters relevant to molten chloroaluminates

Abstract

A model of ionic interactions in neutral and ionized aluminium trichloride clusters, which accounts for ionic deformability through (i) effective valences and (ii) electrostatic and overlap polarizabilities, is evaluated for applications to classical simulation studies of the pure melt and of molten alkali chloroaluminates. The disposable parameters in the model are determined from the measured values of the bond length in the (AlCl4)(-) molecular ion and of an Al-Cl bond length and a vibrational frequency in the Al2Cl6, molecular dimer. The model is tested against the remaining available data from experiment and from quantum chemical calculations on molecular bond lengths, bond angles and vibrational frequencies for Al2Cl6, (AlCl4)(-) and (Al2Cl7)(-) clusters. Structural and dynamical properties are also evaluated for the (Al2Cl5)(+), AlCl3 and (AlCl2)(+) clusters. The results for the energetics of dissociation, ion transfer and isomer excitation reactions are compared with as yet unpublished data obtained by P. Ballone in first-principles calculations by a density functional method. The overall quality of the tests supports the approximate validity and transferability of the model.