Structural transformation and thermodynamics of alloying CunAg55-n(n = 0–55) clusters on cooling from atomic simulations

Abstract

Molecular dynamics simulations were performed to investigate the freezing process of CunAg55-n (n = 0–55) alloying cluster at the atomic scale. Potential energy and shape factors indicate the structural transformation accompanying with the atom motion. Pair-distribution function gives different atomic packing characteristics of some typical structures. Entropy combined with BP neural network is used to analyze the disorder degree of atomic packing in the binary alloying clusters as well as the influence of the number of Cu atoms on the entropy values. The simulation results show that the clusters having fewer or quantity Cu atoms prefer the perfect core–shell icosahedral structures at room temperature. Significant composition effects can be observed during cooling the small size alloying clusters. With changing compositions and decreasing the temperature, the packing structures change from disorder to order accompanying with the changes of atomic energy, shape factor, pair distribution functions, and entropy. In the restricted composition space having 55 atoms, the structure of the melt has an effect on the structural transformation during cooling and the room temperature structure.