Theoretical Study On The Structure And Properties Of Transition Metal And Rare Earth Metal Doped Al₁₂ Clusters

Atomic cluster science is a frontier cross discipline between chemistry and physics,and is currently a quite active research topic.Atomic clusters refer to nanoscale aggregates composed of several to several hundred atoms.They have specific atomic composition and geometric structure,which can be accurately calculated in theory,and can be well characterized in experiment.In recent years,aluminum clusters with special properties have received extensive attention from researchers.It has been reported that the Al^-₁₃ cluster has a fully filled electron shell,a highly symmetrical geometric structure,and special stability,and consequently,show"superatomic"characteristics.On the basis of this research,theoretical and experimental researchers also paid attention to various doped aluminum clusters and have investigated the growth mode,stability,the relationship between geometrical and electronic structure and physicochemical properties of these species.Based on density functional theory（DFT）calculations,this work systematically studied two kinds of aluminum clusters doped with d-zone element hafnium and f-zone element cerium,respectively,namely Al₁₂X（X=Hf,Ce）.Results show that the ground states of Al₁₂Hf and Al₁₂Ce are of singlet and triplet states,respectively,and both structures exhibit an icosahedral configuration,in which the heteroatom X occupies a vertex of the icosahedron.According to the analysis and comparison of the vertical ionic potential,average atomic binding energy,HOMO-LUMO energy gap and other properties of the Al₁₂X system,it can be found that the introduction of dopant atoms makes the system more stable than the host Al₁₃ and Al₁₂ clusters.Molecular orbital calculations reveal that the Hf atom contributes 4 valence electrons in the Al₁₂Hf cluster,so that the entire system has 40 valence electrons,which satisfies the full-shell electron arrangement and becomes a magic number cluster,showing special stability.In contrast,due to the shielding from 5s5p orbitals,the 4f electron of Ce tends to be localized on the atom and does not participate in cluster bonding.Therefore,the ground state structure of Al₁₂Ce has 39 valence electrons,and its corresponding anion has 40 valence electrons,which satisfies the electron arrangement of the magic number cluster,and thus has better stability.In addition,we analyzed the density of states and spectral properties of the Al₁₂X（X=Hf,Ce）clusters.These results help to deepen understanding of the 40 valence electron systems,and provide a theoretical basis for future in-depth study of aluminum-based clusters...