Molecular Dynamics Studies On Cu-based Mixed Clusters

As aggregate in microscopic or submicroscopic level, cluster is constructed byseveral to hundreds of millions atoms or molecules through physical or chemicalinteraction. It plays an important role in nano materals and its properties are related toboth size and element. There are notably different thermal properties between clustersand crystalline materials. Normally, the melting point of a cluster is lower than that ofcrystal, and only in cluster can we find the premelting behavior. Ni, Pd, Pt, Co, Cu, astransition metals, have special physical and chemical characters and importantapplication in magnetism and catalysis ect. Study in38atoms of these pure or mixedsystems is not reported so far.By using genetic algorithm and molecular dynamic simulation method combinedwith Gupta potential, the static and dynamical properties of the38atomic systemsmentioned above are systematically investigated. The conclusion can provide areference to the study of melting behaviors of clusters. The main computationalcontents are as follows,(1) the ground state structures and melting behavior of thepure Ni₃₈, Pd₃₈and Pt₃₈clusters.(2) the same study to Co_nCu_38-n(n=0～38) mixedclusters. We summarize our conclusion as follows:1. All the ground state structures of Ni₃₈,Pd₃₈,Pt₃₈pure clusters have highsymmetry signed as O_h structure, and the excited state called I_h structure. There is anarrow energy gap between the two structures. The melting properties of these threepure clusters are all significant different with the common case, and perform a specialmelting behavior, as there are no obvious wide peaks in their heat capacity curves;Inspite we can't judge their melting points from the heat capacity curves, throughanalysing atomic equivalent index (AEI) curves in different temperatures, we can stillget the melting point.2. The ground state energies of Co_nCu_38-n(n=0～38) mixed clusters aregradually decreasing with adding Co atoms. All the ground-state geometries of themixed systems are O_h structures, except for Co₇Cu₃₁which is I_h structure. The melting points of these mixed clusters are lower than Co and Cu crystalline melting points.There is structure competition during the melting process.