Pt-Au核-壳结构纳米粒子热稳定性的分子动力学研究

Molecular dynamics investigation of thermal stability of Pt-Au core-shell nanoparticle

采用分子动力学方法结合嵌入原子势,对Pt-Au核-壳纳米粒子的热稳定性进行了研究.计算结果表明:Pt-Au纳米粒子的熔点明显高于Au纳米粒子而低于Pt纳米粒子.通过计算Lindemann指数发现:壳层中的Au首先熔化,然后逐渐向内部扩展,最终导致核中的Pt完全熔化;熔化所经历的温度区间明显宽于单质纳米粒子,而且该熔化过程呈现典型的两阶段熔化特征;在两次熔化之间,存在着固(核)液(壳)共存的结构.

In this paper, we have examined the thermal stability of Pt-Au core-shell nanoparticle by using molecular dynamics simulations with embedded-atom potential. The results show that the melting point of Pt-Au core-shell nanoparticle is significantly higher than that of pure Au one but lower than that of Pt one. By the analyses of Lindemann index, it is discovered that the melting first occurs in Au shell, then spreads into interior, finally the overall melting of Pt core appears. The temperature range of melting is much broader for Pt-Au core-shell nanoparticle than for Au and Pt nanoparticles. Moreover, Pt-Au core-shell nanoparticle exhibits a distinct two-stage melting during continuous heating, and the structure of solid （core）-liquid （shell） coexistence has been observed between two meltings.