The Research On The Structures And Adsorption Properties Of Al-Base Alloys Clusters

Atomic clusters is the bridge between microscopic atoms or molecules and macroscopic condensed matters, and aluminum clusters is a hot topic in cluster physics. Aluminum is widely used in electrical industry, mechanical manufacturing, electronics industry, construction industry, as well as aviation, aerospace, shipbuilding and other fields. In different areas the aluminum need different nature, different applications makes the aluminum in different environment. So it is important to study aluminum clusters and the absorption properties.In this paper, the geometries of pure aluminum clusters were optimized by DFT, the lowest energy configuration of clusters was obtained, and then the magnesium atom and lithium atom substituted the aluminum atom on each possible site of the pure aluminum cluster. Then, calculated the relative stability of the system of clusters and their electronic properties, investigated the impact of doping atoms on the clusters. The geometries of pure aluminum clusters we calculated are in agreement with several other first-principles studies. The geometries of magnesium-doped aluminum clusters are similar to the geometries of the corresponding pure aluminum clusters except Al11Mg. The geometries of lithium-doped aluminum clusters are different with pure aluminum clusters, for clusters containing five to seventeen, the structures characteristic of the lowest energy isomers are three-dimensional. Doping magnesium atom and lithium atom reduce the binding energy of pure aluminum clusters, but do not change the trends which the binding energy increases with size. Al7, AL6Mg and Al13Li are most stable in their own systems and they have week activity. In the magnesium-doped and lithium-doped clusters, the magnesium atoms and lithium atoms play the part of donor atoms, electrons transfer from the Mg atom and Li atom to the main Al clusters, making the Mg atom and Li atom with a positive charge, and the Mg atom loses more electrons than Li atom.The hybrid density functional method B3LYP was used to calculate the absorption properties of Al12Li cluster. And the binding energy, stability, adsorption energy, energy gap, the change of bond length was investigated. The strengths of Al12Li cluster adsorbed small molecules follow the order O2> NO> CO> H2> N2; the bond length of small molecules increased after adsorption, and molecules were activated, the H-H and O-O bonds ruptured, these adsorption are dissociative adsorption. Binding energy can reflect the stability, the stability follow the order O2> CO> N2> NO> H2. Energy gaps can reflect the chemical stability, the adsorption of NO and H2 enhanced chemical stability, decreased the chemical activity, the adsorption of CO, O2 and N2 reduced the chemical stability of clusters, and enhanced chemical activity. Considered charge transfer, the small molecules are all acceptors except N2, electrons transfer from clusters to molecular. Considered charge distribution, charges concentrated in small molecular and the center aluminum atom of clusters.