Study Of Modified Embedded-atom Potential For The AlN/TiN System

Superhard nano-multilayer film that have the excellent mechanical properties, and can be designed, and is one of the most promising tool coating material, attract much attention. However, it has been unclear for the hard mechanism of the multilayers of superhard nano-induced, which severely constrains the further development of this field, so this not only as a research topic of great scientific value, but also has high practical application value.Theoretically, one of the effective means to study the nature of the coating material is molecular dynamics simulations. Important prerequisite of molecular dynamics simulations is to understand the interaction potential between atoms. It is widely used that the embedded atom potential(EAM) based on density functional theory, which has achieved great success in the nature of the simulation system on metals and alloys. However, for compounds, EAM potential have a big limitation especially covalent compounds. Therefore, Baskes et al proposed a modified EAM potential(MEAM), so that the potential of EAM application has been further expanded. So far, MEAM potential for most pure elements system have been determined, but the potential MEAM for compound has been studied only a small number. Al N/Ti N multilayers(one possible superhard nano-multilayers) for the study, This paper will determine the MEAM potential of this system between atoms, which is the foundation for further study of molecular dynamics.Inside the Al N monolayer film, the potential between atoms involves Al-Al, N-N, Al-N, interaction between atoms; Inside the Ti N monolayer film, the potential between atoms involves the interaction of Ti-Ti, N-N, Ti-N; In the interface of the between Al N and Ti N layers, in addition to several listed earlier interaction potential, it also involves the interaction between Al-Ti atoms. The MEAM potentials of Al-Al, N-N, Ti-Ti between atoms has been determined, The MEAM potential of Ti-N has also been studied, and therefore the focus of this study is to determine the MEAM potential of Al-N and Al-Ti. The basic idea is: the experimental values of the elastic constants of the binary system(or first-principles calculation value) as the objective function, it can be used to determined MEAM potential parameters(a total of 17, five parameters are input parameters, another 12 parameters are unknown), The optimized potential parameters can be used to verify the other physical properties calculated using MEAM. Finally, the potential MEAM obtained based on the relevant binary system, MEAM potential parameters of ternary system can be obtained.The main contents and results are as follows:1) As a validation of research methods, The MEAM potential for Ti N system was also studied. The Na Cl-Ti N structure(B1-Ti N) elastic constant as the objective function, we optimize 12 pending potential parameters for Ti N system. Using optimized potential parameters, we calculated CSCl Ti N structure(B2-Ti N) elastic constants. In addition to C12 larger differences, the results obtained with the experimental data and first-principles calculation results are in good agreement;2) The B1-Al N elastic constant as objective function, we optimize 12 pending potential parameters for Al N system. Using optimized potential parameters,we calculated the elastic constants of sphalerite structure of Al N(B3-Al N). In addition to relatively larger differences in C44, the other elastic coefficient are in good agreement with the experimental values and the first-principles calculation results;3) The B2-Al Ti elastic constant as objective function, we optimize 12 pending potential parameters for Al Ti system, and verify the parameters from the perspective of the structural stability. On this basis, combined with the results previously obtained, we determine the six pending potential parameters of Al-N-Ti ternary system.