CoCu双金属纳米粒子的聚集与核壳结构模拟研究

The Molecular Dynamics Study of CoCu Bimetallic Nanoparticles Coalescence and Core-Shell Structure

从微观上理解CoCu金属纳米粒子的热力学行为对其在纳米催化领域的应用具有重要意义.该文采用分子动力学结合嵌入原子势的方法对CoCu双金属纳米粒子的聚集与核壳熔化行为进行研究,当温度为300 K和700 K时,由HCP结构组成的原子层贯穿整个Cu纳米粒子并形成层错.当温度为500 K时,由于原子重排引起的层错诱导了金属Cu纳米粒子由FCC结构向HCP结构的转变.进一步升高温度至900 K,可通过聚集形成CocoreCushell结构.对半径R=3 nm的Co、Cu、CocoreCushell和CucoreCoshell纳米粒子的熔化行为进行研究发现,与单金属纳米粒子的熔化相比,CocoreCushell和CucoreCoshell纳米粒子分别经历了从表面到内部和从内部到表面的熔化过程.

The CoCu alloy is one of the most promising catalysts for the synthesis of higher alcohols.It is of considerable significance to understand the thermodynamic behavior of CoCu nanoparticles at the micro-level for their application in the field of nano-catalysis.In this paper,the process of coalescence and core-shell structure melting of CoCu bimetal nanoparticles have studied by molecular dynamics combined with embedded atomic potential.In the process of CoCu nanoparticles coalescence,when the temperature is 300 K and 700 K,the atomic layer composed of HCP structure runs through the whole Cu nanoparticles and forms stacking faults.When the temperature is 500 K,the stacking fault induced by atom rearrangement induces the transformation of Cu nanoparticles from the FCC structure to the HCP structure.Further increasing the temperature to 900 K,the CocoreCushell structure has formed by coalescence.On this basis,the melting behaviors of Co,Cu,Cocore/Cushell,and Cucore/Coshell nanoparticles with radius R=3 nm were further studied.The results showed that compared with the melting of pure metal nanoparticles,Cocore/Cushell,and Cucore/Coshell nanoparticles experienced a two-stage melting process from the surface to interior or interior to surface respectively.From the atomic point of view,this study provides a fundamental perspective on the coalescence and melting behavior of bimetallic(even multi-metallic)nanoparticles.