Dislocation nucleation in a thin Cu film from molecular dynamics simulations: Instability activation by thermal fluctuations
Dislocation nucleation in a thin Cu film from molecular dynamics simulations: Instability activation by thermal fluctuations
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DOI：
10.1103/physrevb.82.104108
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发表时间：
2010-09
影响因子：
3.7
通讯作者：
Y. Umeno;T. Shimada;T. Kitamura
中科院分区：
文献类型：
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作者：
Y. Umeno;T. Shimada;T. Kitamura
为了从原子水平上阐明结构不稳定性的机制，采用嵌入原子法势对含缺口的Cu薄膜进行了拉伸的原子模型模拟，观察到了位错形核.通过求解海森矩阵的本征值问题，考虑系统中原子的所有自由度，分析了拉伸过程中的机械稳定性。由于本征值表示在对应的本征向量方向上的势能景观的曲率，其指示变形模式，因此当任何本征值为零或负值时，系统在临界应变（cid：1）（cid：1）c（cid：2）处的消失温度下是不稳定的。在应变小于（cid：1）c时，所有本征值都为正值，由于有限温度引起的原子涨落可能导致结构不稳定。我们发现，激活不稳定性（cid：1）位错从缺口（cid：2）发射的路径可以写在一个线性组合的本征向量具有小的本征值下得到相应的外部应变在零温度。能源景观有一个低得多的山丘沿着混合模式的路径比沿着任何单一模式的路径。在有限温度下的分子动力学模拟中，具有小特征值的变形模式的分量在低频下波动，这主导了不稳定性的激活。DOI：10.
To elucidate the mechanism responsible for structural instability at the atomic level, atomistic modeling simulation of tension in a Cu thin film containing a notch was performed using an embedded-atom method potential and dislocation nucleation was observed. Mechanical stability during tension was analyzed by solving the eigenvalue problem of the Hessian matrix taking into account all the degrees of freedom of the atoms in the system. Since an eigenvalue designates the curvature of the potential energy landscape in the direction of the corresponding eigenvector, which indicates a deformation mode, the system is unstable under vanishing temperature at the critical strain (cid:1) (cid:1) c (cid:2) when any eigenvalue is zero or negative. At a strain smaller than (cid:1) c where all the eigenvalues are positive, atomic fluctuations due to finite temperature may cause structural instability. We found that the path of activated instability (cid:1) dislocation emission from the notch (cid:2) could be written with a linear combination of the eigenvectors having small eigenvalues obtained under a corresponding external strain at zero temperature. The energy landscape has a much lower hill along the mixed-mode path than along any single-mode paths. In a molecular dynamics simulation under finite temperature, components of deformation modes having small eigenvalues fluctuate at low frequency, which dominate the activation of instability. DOI: 10.