Simulation Study Of Multimetallic Clusters For Structural Stability

At present,the multimetallic clusters have attracted extensively attention in nanomaterial research fields.The structural optimization problem is quite difficult because the large number of local minima tends to grow exponentially with system size.In this paper,in addition to using the global optimization algorithm to optimize the multimetallic clusters,an improved algorithm for adaptive immune optimization(AIOA)is proposed.The regularity of structure and properties of multimetallic clusters were studied by using global optimization algorithm as an analysis method.Specifically,the main contents of this thesis can be summarized as follows:1.The interatomic interactions between clustersclusters of metal atoms are described by the Gupta potential.Global optimization of 38-atomAu-Pd-Ptclusters is performed using AIOA algorithm.Results show that these global minimum structures include Marks decahedra,partial Mackay icosahedra,complete truncated octahedra,stacking fault face centered cubic,and amorphous motifs.Furthermore,the segregation phenomena of Au,Pd,and Pt were analyzed in Au-Pd-Pt clusters.It was found that Au and Pt atoms tended to belocated on the surface and in the inner shell,respectively,and more Pd atoms preferred solving into Au atoms than Pt atoms.Moreover,From clusters structural stability,the relative stability of trimetallic clusters was studied by thesecond order finite difference and excess energy.2.Global optimization of M-Pd-Pt(M=Ag and Au)clusters with up to 75 atoms is performed using AIOA.The structures and properties of bimetallic Pd-Pt clusters are affected by different types the metal dopants in trimetallic M-Pd-Pt(M=Ag and Au)clusters.The structures of 13-atom M-Pd-Pt(M = Ag,Au)clusters are present in the form of icosahedral and non-icosahedron,and the number of non-icosahedra in Au-Pd-Pt clusters is larger than that in Ag-Pd-Pt clusters.Moreover,the atomic distribution patternof Pd and Pt atoms in Ag-Pd-Pt clusters is similar to that in Au-Pd-Pt clusters,but the Au atoms grow more aggregated than the Ag atoms.The relative stability for both clusters is compared by the second order finite difference parameter.3.An improved AIOA algorithm is proposed,and the modified AIOA is called AIOA-BDLS-ILS method.The efficiency of the algorithm is tested by the binary LJ model.Compared with previously reported BDLS-ILS method,the proposed method is more efficient.For 34-atom bimetallic Pd-Pt clusters,12 lower energy structures were found.In addition,50 and 79 atoms were optimized.Moreover,the order parameter show that there exists the segregation phenomenon of Pd and Pt atoms in Pd-Pt clusters.