Study on the geometric structure and stability of AlnMgn (n = 2–12) clusters using density functional theory

Abstract

In this study, density functional theory was used to investigate the AlnMgn (n = 2–12) clusters on a microscopic scale. The stable structure of clusters was determined and used as the interaction energies parameter in Wilson equation to deepen the activity prediction of the Wilson equation. The properties of Mg2 and Al2 dimers calculated by using ab initio molecular dynamics were compared with experimental data to verify the reliability of the method. By characterizing the cluster structure, the average binding energy, fragmentation energy, second–order energy difference, vertical ionization potential, vertical electron affinity, chemical hardness, HOMO–LUMO gaps, and distribution of the Al–Mg clusters were determined. With an increase in the cluster size, the symmetry of the Al–Mg clusters decreased, and Al atoms gradually gathered at the center of the cluster, whereas Mg atoms were distributed on the surface of the cluster, which tended to combine with Al atoms. Clusters with even numbers were generally more stable than the adjacent odd–numbered clusters. In particular, the thermodynamic stability of the Al4Mg4 cluster was prominent and was considered as an ideal object to calculate the interaction energies in the activity prediction of Al–Mg alloys.