Molecular Dynamics Simulation Of Atomic Diffusion At The Interface Between CoSb₃and Ti

Due to global energy crisis in recent years, the study on thermoelectric conversion technology and high performance thermoelectric materials have attracted many people of great concern.CoSb3is one of the promising thermoelectric materials in the moderate and high temperature range, but if it widely used to people’s daily lives, It will encounter a lot of problems. The connection problem between CoSb3and electrode material’s interface is very important. In the interface between CoSb3and electrode material, diffusion in the interface has happened. With time increase, three-layer intermetallic compound (IMC) structure was observed at the CoSb3/Ti interface, and the total thickness of IMC layers increased with the use time. It last it leads to interfacial debonding. This problem has greatly impact on the widely application of thermoelectric materials. So the study of the process and critical condition of diffusion at the CoSb3/Ti interface becomes very important. Therefore, we study the process and critical condition of diffusion of the CoSb3/Ti interface at different temperature by molecular dynamics method, which provides references to the service behavior and the preparation of the electrode of thermoelectric materials.The diffusion of CoSb3/Ti interface are studied by molecular dynamics method through open-source parallel program Lammps. The main content is as follows:1、Through consulting the relevant literature, the master orientation and the atomic configuration at the CoSb3/Ti interface are obtained, and the atomic model of the interface is constructed.2、lastic constants, surface energy, and interfacial energy are several fundamental physical quantities which characterize the properties of materials and their interfaces. These quantities should be represented accurately by the correct potential function. Hence we make evaluations on several potential functions, and select precise ones. Based on the consideration of atomic bonding, with the results about the atomic interactions at the interface derived from experiments and theories, then the expressions of potential function are determined. With the first-principle results on interfacial energy to be the reference value, the parameters and thus the potential itself are obtained by function-fitting. Finally, the relevant potential functions have been validated from structural stability to configuration of interface atoms.3、The CoSb3/Ti interfacial diffusion model has been simulated by molecular dynamics method under300K、500K、800K. in order to make diffusion more likely to occur, we use the existence of vacancies in CoSb3interface model, as well as the vacancies exist in Ti interface model to simulate the diffusion process, and by calculating the mean square displacement and compared the rate of diffusion of several different models at different temperatures, in order to find the model and temperature which more prone to the diffusion. We find that the models which containing vacancy are more easily occur diffusion than the models without vacancy. And the occurrence of interatomic diffusion at300K is difficult to find, when the simulation temperature of500K, the model of the atom with vacancy began to diffusion, when the temperature increase to800K, diffusion even faster. This diffusion is mainly caused by thermal vibrations of atoms.