Bi_2Te_3纳米薄膜单轴拉伸的分子动力学模拟

Molecular Dynamics Simulation of Bi_2Te_3 Nanofilm Under Uniaxial Tension

Bi2Te3及其合金是目前室温附近发展最为成熟、性能最好的一类热电材料,在热电制冷及温差发电方面具有广阔的应用前景。具有纳米结构的Bi2Te3纳米薄膜材料是当前研究的热点,其力学性能是热电材料研究者较为关心的问题。依据Bi2Te3多体势函数利用分子动力学方法对Bi2Te3单晶块体沿c轴方向进行单轴拉伸模拟。拉伸之前对系统进行弛豫,考察了弛豫过程中系统能量、温度和初始应力的变化。根据原子构型发现在此方向上拉伸过程中薄膜沿着晶体中结合力较弱的Te1-Te1层断开。分析了拉伸过程中的应力-应变和能量变化曲线。模拟不同温度下的拉伸,研究了温度效应对其力学性能的影响。

Bi2Te3 and its alloys are the best thermoelectric material at room temperature and have been used in many practical applications due to its good thermoelectric performance. Nanostructured materials such as Bi2Te3 nanofilms have attracted considerable attention. The researchers are concerned about its mechanical performances. With the use of many-body potential, a molecular dynamics simulation of the uniaxial tension deformation has been carried out to evaluate the mechanical properties of Bi2Te3 nanofilm along the c axis. Before tension, temperature and stress evaluation of the system have been studied. Simulation results show that along the c axis the fracture occurs along the adjacent Tel-Tel layers, which responds to the ease of cleavage along the planes. We also analyzed the stress-strain and energy curves during the deformation, and investigated the effects of temperature on the uniaxial tension of Bi2Te3 nanofilm.