Density Functional Study Of Al_nZr(n=1-14) And Al_xZr_y(x+y≤9) Alloy Clusters

The past few decades have witnessed a transition from studying pure clusters to binary clusters in the field of cluster science.In particular,more efforts have been devoted to studying the bimetallic atomic clusters.By adding a second element to monoatomic clusters,the mutual influence of the two components introduces additional parameters and leads to the unique physical and chemical properties of this kind of system,such as enhanced stability by suitable mixing and exhibits unusual electronic,optical,magnetic and catalytic properties.Aluminum and Zirconium are the two important metallic materials,and the Al-Zr alloys are considered as prospective candidates for structural materials used in thermal nuclear reactors and aerospace fields due to a number of excellent properties,such as high strength and toughness,good corrosion resistance.Although the binary Al-Zr alloy phase has been well understood,the research on nanoalloying at the nanoscale remains scarce.By exploring the structure and properties of Al-Zr nanoclusters,it may be possible to synthetise cluster-assembled materials with special functions.So in this paper,we investigated the geometrical structures and properties of Al_nZr(n = 1-14)and Al_xZr_y(x + y ≤ 9)clusters using density functional theory.The main results are as follows:Firstly,we studied the change rules of the structural stability,electronic and magnetic properties of the single doped Al_n Zr(n = 1-14)clusters with the cluster size.The calculations show that Zr substituted Al_n+1 clusters or Zr capped Al_n clusters as well as Al added Al_n-1Zr clusters are the dominant growth patterns,and the Zr atom prefers to reside at the surface of the Al_nZr(n = 1-14)clusters.An analysis of the relative stabilities shows that the Al_nZr(n = 4,6,8,10 and 12)clusters are more stable than neighboring clusters.There exits s-p hybridization in Al atom and sp-d hybridization in Zr atom.In addition,in all Al_nZr clusters the charges are obviously transferred from Al atoms to Zr atom caused the s-d hybrid,which strengthens the interactions of Al-Zr.The magnetic calculations show that,for the Al8 Zr,Al10Zr and Al12 Zr clusters,their total magnetic moments are all zero because all the electrons are paired in their molecular orbital;while for other Al_nZr clusters,the 4d electrons of Zr atom are the main origin for cluster magnetism.Next,we discussed the properties of mixed Alx Zry(x + y ≤ 9)clusters and found that the structures of bimetallic clusters prefer to form the same motif as their corresponding pure Al or Zr clusters.The total magnetic moments depend not only on the configuration but also on the composition of the clusters.Our results of stabilities shown a favorable mixing for all clusters and the clusters with about equal Al:Zr ratios exhibit higher stability than other neighboring clusters for a given cluster size.With the increase of cluster size,chiral structures exist in the mixed clusters with x + y = 6,8 and 9.Computations of VCD and ROA spectra confirmed the chirality of the resulting enantiomers.We hope that this work of bimetallic Al_xZr_y clusters combining magnetism and chiral features could offer some guidance for further synthesis of functional materials which has interesting optical applications.