Theoretical Study On The Structure, Stability And Electronic Properties Of Al-Mg Clusters

Metal alloys composed of aluminum and magnesium have been widely recognized to be of importance in aerospace manufacturing and other industry, They are not only cheaper and lighter than other aluminum alloys but also have good electrical conductivity and corrosion resistance. In this paper we studied the stability and electronic properties of Magnesium doped Aluminum clusters. The global lowest energy structures of Al_nMg_m?n=4-8,m=1-3? clusters are searched by using genetic algorithm combined with Modified embedded-atom method interatomic potential?Meam?, the stability and electronic structure is further studied by using density functional theory?DFT?. We adjusted some parameters of the Meam potential and get the most stable structures in the literature, meamwhile, we have given some lower energy isomers. It means that the Meam potential can offer proper description to the interaction between aluminium and magnesium atoms.The present study indicates that Al_nMg_m clusters have a few isomers with close energies. The interaction between Mg atoms is weaker than the interaction between Al atoms and magnesium atoms tend to form more Al-Al bonds in the stable structures. The study shows that doping Mg into Aluminum clusters will decrease the stability slighter. the electronic structure of clusters are analyzed by NBO charge, HOMO-LUMO gap, the density of states?DOS? and molecular orbitals. NBO charge indicates that magnesium transfer electrons to aluminum, and the charge on Al atoms depends strongly on the number of the connected Mg atoms. Analysis on the electronic structure shows that the energy levels of occupied orbitals decrease slightly with the increase of the cluster size. the HOMO–LUMO gaps are in the range of 1.57 eV to 2.83 eV. Molecualr orbitals show that the Al₆ Mg cluster have closed electronic shells, the Al₆ Mg cluster with 20 valence electrons exhibit enhanced stablility and have the greatest energy gap, so it is of strong chemical stability.