Molecular Dynamics Simulation Of The Alloying Behavior Of Li/Pb Nanoparticles

Alloy nanomaterials have become one of the hot issues in the field of materials research because of its particular physical and chemical properties.In the process of preparation of alloy nanomaterials,how to control the size,the proportion of constituents and the special structure of nanoparticle have become the basic and important subjects of alloy nanomaterials research.Exploring the alloying process and mechanism of nanoparticles can help us better grasp the regularities of the formation of alloy nanoparticles,improve the preparation technology of alloy nanomaterials and develop new-type alloy nanomaterials.In this paper,we applied molecular dynamics(MD)simulation method with modified analytic embedded-atom method(MAEAM)to simulate the alloying behavior of Li/Pb nano system and studied the evolution regularities of the microstructure,sintering ability and alloying degree of Li/Pb nano system with dumbbell-shape and core-shell configurations in the sintering-alloying process,revealing the effects of the ambient temperature,the size and particular configuration of nanoparticles on alloying behavior.Firstly,we discovered that the relatively stable configurations of Li and Pb nanoparticles are truncated rhombic dodecahedron(TRHO)and truncated octahedron(TO)when they are larger than 1000 atoms by investigating the structural thermostability of their individual nanoparticles,respectively.Simultaneously,the relationships between melting temperature and size of Li TRHO and Pb TO nanoparticles were explored,and the results are in well agreement with the values in the thermodynamic model study and the experiment.Secondly,the alloying process of Li-Pb nano system with dumbbell-shape configuration was researched,and we observed that the higher the temperature and the smaller the nanoparticle size is,the stronger the sintering capacity,the easier the appearance of alloying behavior,the more obvious the alloying phenomenon and the higher the alloying degree is.Besides,the alloying process of Li and Pb nanoparticles is mainly through the mutual diffusion of Li and Pb atoms along the direction vertical to the interface and the alloying product B2-Li Pb tends to nucleate near the surface layer of the mixed region of Li and Pb nanoparticles as results of the surface segregation of Pb atoms.Consequently,a stable alloy nanoparticle dominated by Pb atoms at surface layer is formed.Thirdly,the effects of temperature and the thickness of Pb shell on the sintering alloying process of Li/Pb nano system with the core-shell structure were researched.Our findings show that the higher the temperature and the higher the alloying degree is,the easier the formation of alloying product is.In terms of the effect of the thickness of Pb shell,with the increase in thickness of Pb shell,the alloying degree enhances at first and then decreases,while the alloying product B2-Li Pb decreases firstly and then increases and the rate of decrease is much greater than the rate of increase,and it’s worth noting that when the thickness of Pb shell is thick,the representative stacking fault phenomenon is observed due to the mutual diffusion of Li and Pb atoms at the interface of Li core and Pb shell.Fourthly,we contrastively analyzed the alloying processes for the different structures and systems.The alloying process presents the different features with the different sintering model and system.It is hopeful that the study on the alloying behavior of Li/Pb nanoparticles systems in this paper can provide good theoretical guide to the preparation technology and development of alloy nanomaterials.