Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion
Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion
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DOI：
10.1103/physrevb.96.054118
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发表时间：
2017-08-29
影响因子：
3.7
通讯作者：
Xiong, Liming
中科院分区：
文献类型：
--
作者：
Levitas, Valery I.;Chen, Hao;Xiong, Liming
针对任意应力张量和大应变的一般载荷，开发了一种用于预测晶体-晶体相变 (PT) 期间晶格不稳定性的连续体/原子方法。它基于广义朗道型 PT 理论和分子动力学 (MD) 模拟的协同组合。连续介质方法用序参数描述了整个耗散转变过程，并利用热力学第二定律导出了不稳定准则的一般形式。 MD 的反馈使我们能够根据修改后的变换功的临界值提出直接和反向 PT 的不稳定性准则，该临界值与真实应力张量的分量呈线性关系。它通过 MD 模拟在两种不同应力状态下对半导体硅 Si I 和金属 Si II 相之间的直接和反向 PT 进行校准。然后，它描述了在三种法向应力和三种剪切应力的各种组合下的数百个 MD 模拟。特别是，原子模拟表明，沿立方轴的所有三个剪切应力对 Si I 晶格不稳定性的影响都可以忽略不计，这与我们的标准一致。
A continuum/atomistic approach for predicting lattice instability during crystal-crystal phase transformations (PTs) is developed for the general loading with an arbitrary stress tensor and large strains. It is based on a synergistic combination of the generalized Landau-type theory for PTs and molecular dynamics (MD) simulations. The continuum approach describes the entire dissipative transformation process in terms of an order parameter, and the general form of the instability criterion is derived utilizing the second law of thermodynamics. The feedback from MD allowed us to present the instability criterion for both direct and reverse PTs in terms of the critical value of the modified transformation work, which is linear in components of the true stress tensor. It was calibrated by MD simulations for direct and reverse PTs between semiconducting silicon Si I and metallic Si II phases under just two different stress states. Then, it describes hundreds of MD simulations under various combinations of three normal and three shear stresses. In particular, the atomistic simulations show that the effects of all three shear stresses along cubic axes on lattice instability of Si I are negligible, which is in agreement with our criterion.