Molecular dynamics at constant Cauchy stress,The Journal of Chemical Physics

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Molecular dynamics at constant Cauchy stress
The Journal of Chemical Physics ( IF 3.1 ) Pub Date : 2016-05-11 14:08:08 , DOI: 10.1063/1.4948711
Ronald E. Miller ₁ , Ellad B. Tadmor ₂ , Joshua S. Gibson ₁ , Noam Bernstein ₃ , Fabio Pavia ₄

Affiliation

The Parrinello-Rahman algorithm for imposing a general state of stress in periodic molecular dynamics simulations is widely used in the literature and has been implemented in many readily available molecular dynamics codes. However, what is often overlooked is that this algorithm controls the second Piola-Kirchhoff stress as opposed to the true (Cauchy) stress. This can lead to misinterpretation of simulation results because (1) the true stress that is imposed during the simulation depends on the deformation of the periodic cell, (2) the true stress is potentially very different from the imposed second Piola-Kirchhoff stress, and (3) the true stress can vary significantly during the simulation even if the imposed second Piola-Kirchhoff is constant. We propose a simple modification to the algorithm that allows the true Cauchy stress to be controlled directly. We then demonstrate the efficacy of the new algorithm with the example of martensitic phase transformations under applied stress.

中文翻译：

恒定柯西应力下的分子动力学

用于在周期性分子动力学模拟中施加一般应力状态的Parrinello-Rahman算法已在文献中广泛使用，并已在许多容易获得的分子动力学代码中实现。但是，经常被忽略的是，该算法控制第二个Piola-Kirchhoff应力，而不是真正的（Cauchy）应力。这可能会导致对模拟结果的误解，因为（1）在模拟过程中施加的真实应力取决于周期晶胞的变形；（2）真实应力与施加的第二Piola-Kirchhoff应力可能存在很大差异，并且（3）即使施加的第二Piola-Kirchhoff是恒定的，在仿真过程中，真实应力也会显着变化。我们对算法提出了一个简单的修改，允许直接控制真正的柯西应力。然后，我们以施加应力下的马氏体相变为例，演示了新算法的有效性。

更新日期：2016-05-12

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