高指数晶面Au-Pd纳米合金粒子的稳定结构研究

Investigation on stable structures of Au-Pd alloy nanoparticles with high-index facets

基于蒙特卡罗方法,本文采用了紧束缚势和量子修正Sutton-Chen型多体势两种势能函数对具有不同比例、不同尺寸二十四面体Au-Pd合金纳米粒子的稳定结构、表面原子分布、核壳分布和化学短程序值进行了研究分析.结果表明:两种势函数得到的表面原子分布趋势一致,即Au-Pd合金纳米粒子中的Au原子趋向于分布在纳米粒子的外层,而Pd原子趋向于分布在纳米粒子的内层,这有利于降低纳米粒子的总能;在Au原子比例较小时,两种势函数下得到的稳定结构均呈现出核壳分离的结构,随着Au比例的增大,紧束缚势函数下得到的纳米粒子稳定结构将趋向于洋葱状的多壳层的结构;相比于紧束缚势,量子修正Sutton-Chen型多体势作用下得到的Au-Pd纳米粒子的稳定结构偏聚程度更高.

Based on the Monte Carlo simulation method, this paper employs the tight-binding potentials and the quantum- corrected Sutton-Chen type many-body potentials to investigate the stable structure, the distribution of surface atoms, the core-shell distribution, and the chemical short-range order parameter of tetrahexahedral Au-Pd nanoparticles. Dif- ferent sizes and different Au contents are considered. Our results show that the surface atom distribution exhibits the same trend for the two types of potentials, that is, Au atoms tend to segregate on the surface while Pd atoms prefer to occupy the inner sites, this is beneficial to lowering the total energy of the structure. Nanoparticles are always present in a core-shell structure for small ）~u content. With increasing Au content, the Au-Pd nanoparticles will tend to form an onion-like multi-shell structure for the tight-binding potentials. The degree of the segregation of Au-Pd nanoparticles at the quantum-corrected Sutton-Chen type potentials is higher than that for the tight-binding potentials.