淬火制备非晶硅的分子动力学模拟研究

Molecular Dynamics Simulation of Amorphous SiliconPreparation by Quenching

在微机上用分子动力学方法模拟了熔Ｓｉ淬火制备ａ－Ｓｉ的过程。硅原子间的相互作用势采用Ｓｔｉｌｉｎｇｅｒ－Ｗｅｂｅｒ势。受计算量的约束，淬火速度一般很高，此时采用这种势无法直接从熔Ｓｉ得到ａ－Ｓｉ。本文作者采用１０００Ｋ左右的体积一次性膨胀法克服这一困难。对模拟制备的ａ－Ｓｉ的径向偶对分布函数、键角分布函数及配位数的分析表明，ａ－Ｓｉ中的四面体网络结构已得到了比较好的恢复。对制备过程的分析则显示，体积膨胀及随后的弛豫所导致的三体能大幅度下降是使体积一次性膨胀法有效的主要原因。

The preparation of amorphous silicon via quenching the melt has been simulated by molecular dynamics method on microcomputer.StillingerWeber potential has been employed to describe the interaction between silicon atoms.For a very high quench rate which is usually used in simulation due to the limitation of the amount of computer time,it is impossible to obtain amorphous silicon from the melt directly using this potential.In this work,the oneshot volume expansion near the temperature of 1 000 K is taken to solve this problem.The wellrecovered tetrahedral network is evident from the analysis of the radial pair distribution function,the bond angle distribution function and the coordination number of the soprepared amorphous silicon.The analysis of the preparation procedure shows that,the substantial decrease of the threebody energy caused by the volume expansion and the subsequent relaxation process is the main reason of the validity of the oneshot volume expansion method.