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研究了分子动力学模拟中纳米多晶金属样本的构建过程.首先采用Voronoi几何方法生成初始的纳米多晶铝和铜样本,然后用快速冷凝(或共轭梯度)法得到样本的局域最低能态,最后在恒温零应力周围环境下(常温常压NPT系综)退火得到最低能态样本.使用样本的残余内应力来衡量纳米多晶样本是否与实验制备的一致.通过监测这两步弛豫过程中晶界结构的变化形态、体系平均内应力和能量下降过程及具体的局域分布和不同弛豫条件下最终样本的弹性常数,发现样本的能量和残余内应力都接近实验制备的纳米多晶金属.对Voronoi几何法生成的晶界而言,5—10ps的快速冷凝(或共轭梯度法)能量最小化,40—100ps的升温(温度控制在室温到0.65倍熔点)退火较合适,弛豫时间和退火温度选择在一定范围内时对弛豫样品终态的力学性质影响很小.
The construction process of nano-polycrystalline metal samples in molecular dynamics simulation was studied.The initial nano-poly aluminum and copper samples were generated by Voronoi geometry method, then the local minimum energy of the sample was obtained by the method of fast condensation (or conjugate gradient) Finally, the sample with the lowest energy state is annealed under the environment of constant temperature and zero stress (normal temperature and pressure NPT ensemble), and the residual internal stress of the sample is used to measure whether the nano polycrystalline sample is consistent with the experimental preparation. The change of grain boundary structure, the average internal stress and energy descent process, the specific local distribution and the elastic constants of the final samples under different relaxation conditions in the process of Yu show that the energy of the sample and the residual internal stress are close to those of experimentally prepared nano Polycrystalline Metals For the grain boundaries created by the Voronoi geometry, the energy of 5-10 ps for rapid condensation (or conjugate gradient method) is minimized and the 40-100 ps ramp (room temperature to 0.65 times the melting point) , Relaxation time and annealing temperature within a certain range of choice when the end of the relaxation of the mechanical properties of the sample has little effect.