Molecular Dynamics Study Of Mechanical Properties Of Zn₄Sb₃ Thermoelectric Material

In recent years, due to global energy crisis, the study on thermoelectric conversion technology and high performance thermoelectric materials have attracted many people of great concern. Zn4Sb3 material has been recognized as one of the most promising thermoelectric materials, since it shows a high figure of merit value in the intermediate temperature range. However, the unstable mechanical properties and low intensity of the deficiencies of Zn4Sb3 thermoelectric material restrict its wider application to a large extent. Of the material mechanical quantities, ultimate stress and elastic modulus are the basic performance of mechanical strength, which plays an important role in measuring the stability of the thermoelectric material in the process of thermal fatigue and stress fatigue. So, it is very significant to study mechanical behavior of thermoelectric materials. Therefore, we study the basic mechanical properties of Zn4Sb3 single bulk at OK and 300K by molecular dynamics method, which provides references to study the service behavior of Zn4Sb3 single bulk.Mechanical properties of Zn4Sb3 single bulk are studied by molecular dynamics method through open-source parallel program Lammps. The main content is as follows:1. The ground-state physical properties of Zn4Sb3 crystal structure were studied by first-principles method through VASP (Vienna Ab-initio Simulation Package) based on density functional theory. First, we constructed the smallest repeated Zn4Sb3 crystal unit cell model, then the balanced volume, cohesive energy and atomic coordinates were obtained through the optimized crystal structure. Given six different sets of strain to obtain corresponding six groups of independent equations, the Zn4Sb3 elastic constants matrix was obtained through first principles calculation.2. Simplify the complex Zn4Sb3 crystal structure and find out the correct interatomic bond styles among Zn4Sb3 crystal structure. First, we selected a representative Zn4Sb3 crystal structure from several known crystal structures and gave interatomic bond styles and potential energy function. Regarding the ground-state physical properties as input data, the potential energy functional values were obtained from least squares method through fitting equations of the ground-state physical properties.3. According to the characteristics of Zn4Sb3 crystal structure, the single-cell model was constructed for molecular dynamics calculation. The potential energy function was verified from elastic constants at OK and the stability of balanced Zn4Sb3 crystal structure in which the stability was measured by the neighbor atomic distances obtained from radial distribution function. The tensile mechanical properties of Zn4Sb3 single bulk both along [010] and [001] direction were simulated at OK and 300K, respectively. By comparison, the thermal vibration is the main reason to the different mechanical behavior between different temperatures.