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首页> 外文期刊>The Journal of Chemical Physics >Kinetics of phase transformations in a model with metastable fluid-fluid separation: A molecular dynamics study
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Kinetics of phase transformations in a model with metastable fluid-fluid separation: A molecular dynamics study

机译：亚稳态流体-流体分离模型中相变动力学：分子动力学研究

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By molecular dynamics (MD) simulations we study the crystallization process in a model system whose particles interact by a spherical pair potential with a narrow and deep attractive well adjacent to a hard repulsive core. The phase diagram of the model displays a solid-fluid equilibrium, with a metastable fluid-fluid separation. Our computations are restricted to fairly small systems (from 2592 to 10368 particles) and cover long simulation times, with constant energy trajectories extending up to 76 X 10~6 MD steps. By progressively reducing the system temperature below the solid-fluid line, we first observe the metastable fluid-fluid separation, occurring readily and almost reversibly upon crossing the corresponding line in the phase diagram. The analysis of the temperature dependence of the nucleation time allows us to estimate directly the nucleation free energy barrier. The results are compared with the predictions of classical nucleation theory. The critical nucleus is identified, and its structure is found to be predominantly fcc. Following nucleation, the solid phase grows steadily across the system, incorporating a large number of localized and extended defects. We discuss the relaxation process taking place both during the after the crystallization stage. The relevance of our simulation for the kinetics of protein crystallization under normal experimental conditions is discussed.
机译：通过分子动力学（MD）模拟，我们研究了模型系统中的结晶过程，该系统的颗粒通过球对电位与邻近硬排斥核的窄而深的吸引孔相互作用。模型的相图显示了固液平衡，并具有亚稳态的液液分离。我们的计算仅限于相当小的系统（从2592到10368个粒子），并且涵盖了较长的仿真时间，恒定的能量轨迹可扩展到76 X 10〜6 MD步长。通过逐步将系统温度降低到固相线以下，我们首先观察到亚稳态的流体-流体分离，在相图中越过相应的线，该分离就容易且几乎可逆地发生。对成核时间的温度依赖性的分析使我们能够直接估算成核自由能垒。将结果与经典成核理论的预测进行了比较。确定了关键核，并发现其结构主要为fcc。成核后，固相在整个系统中稳定增长，并包含大量局部和扩展缺陷。我们讨论了在结晶阶段之后发生的弛豫过程。讨论了我们在正常实验条件下模拟蛋白质结晶动力学的相关性。

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