Aluminum And Its Alloys Of Nickel Cluster Structure And Nature Of The Pso-sa Simulation

As aggregates of finite number of atoms at the microscopic level, clusters exhibit novel geometries,electronic and magnetic properties as well as widely potential applications.The study of atomic clusters can not only help to making more understanding of native properties of atomic clusters,but also speed learning of properties of solid body.Particle Swarm Optimization is a kind of evolutionary computation based on Swarm Intelligence.It is not only suitable for scientific research but also suitable for engineering application.However,it is not perfect for its precocious convergence and bad local optimization ability.In this dissertation,Particle Swarm Optimization was combined with Simulated Annealing method,which was good at local optimization,to overcome that weakness of Particle Swarm Optimization.In this dissertation,with a particle swarm optimization(PSO) combined with simulated annealing(SA)method,the structures and stabilities of aluminum,nickel and nickel-aluminum nanoalloy clusters were studied modeled by many-body TB-SMA potential and Sutton-chen potential.The electronic structure of Ni-Al clusters were calculated using a first-principles pseudopotential plane-wave method and the Cambridge serial total energy package(CASTEP)and local density functional cacluations on molecules(DMOL~3),the Density of States(DOS)and partial Density of States(PDOS)of Ni,Al and Ni-Al clusters have been investigated.From the PDOS,the interactions of s,p and d electrons,the effect of Ni and Al atom of the NiAl_n nanoalloy clusters were also analyzed.The relation between the number of interations and energies was calculated.The result shows that PSO-SA is good for the global optimization of clusters.The research results of Al and Ni indicate that the structures of clusters are icosahedral-like.The odd-even alternations and magic numbers effect exist in all of them.Because of the presence of the geometrical isomers,it is more difficult to find the lowest energy structure of the nanoalloy clusters than the pure metallic clusters.The structure of the Ni-Al nanoalloy clusters was investigated based on the particle swarm optimization(PSO)combined with simulated annealing (SA)method.It shows that the structure of the lowest energy Ni-Al bimetallic clusters exhibit primarily icosahedral packing.When the number of aluminum atoms is greater than that of nickel atoms,the clusters tend to form layered structures.In the opposite situation,the clusters tend to show random Ni-Al mixing.The analysis of the DOS of Al shows that the increase of stability of Al cluster mainly originates from the enhancement of s-p hybridization.Based on the study of Ni on band structure and DOS,an argument that the d orbit electrons contribute to the energy levels is mainly supported.There is a strong peak near the Fermi level.The PDOS curve is different because of the different element content.The d orbit electrons mainly contribute near the Fermi level.The alloy clusters PDOS mainly s,p orbit before Fermi level,the Ni atoms mainly contribute near Fermi level.The DOS of Ni decreased near Fermi level when one Al atom inserts into NiAl_n cluster from the electronic property research results.