Compare the Energies of Different Structures in Aluminium Electrochemical Cell

Abstract

The fluoroaluminate molten salts are used in the Hall-Heroult industrial process for the production of aluminum by electrolysis. To better understand the mechanism of the dissolution of alumina (Al₂O₃) in cryolitic melts, we have studied the structure stability of these anions The initial structural models of [Al₂OF₆]²⁻, [Al₂O₂F₄]²⁻, [Al₂O₂F₆]⁴⁻ and [Al₂OF₁₀]⁶⁻ were generated using Gauss View Since this study attempts to compare the energies of different oxofluoroaluminum structures, the geometries should be optimized at an accurate level of theory Therefore, geometry optimizations and energy calculations were carried out by B3LYP density functional while several basis sets including 6-31g, 6-311g**, 6-311g** and 6-311++g** were used. Furthermore, solvent effect on structural energies was investigated through incorporation of conductor-like polarizable continuum model (CPCM) at B3LYP/6-311++g** level of theory the structure was optimized at different levels by applying CPCM solvent model. Similar calculations were performed for the other complex structures and similar results were obtained for them. Based on the energy values, the following stability order is achieved: [Al₂O₂F₄]²⁻ < [Al₂OF₆]²⁻ < [Al₂O₂F₆]⁴⁻ < [Al₂OF₁₀]⁶⁻.