arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2001.02224cond-mat.stat-mechphysics.chem-ph
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用分子动力学模拟计算稠密原子流体的平衡三粒子熵

Computation of the equilibrium three-particle entropy for dense atomic fluids by molecular dynamics simulation

Luca Maffioli, Nathan Clisby, Federico Frascoli, B. D. Todd

摘要:

我们用分子动力学模拟计算了两粒子和三粒子对Weeks-Chandler-Andersen流体熵的贡献。用一种新的方法计算了三粒子关联函数和熵,简化了计算。结果定性类似于Lennard-Jones系统。我们观察到的三粒子贡献的数值不稳定性。当使用传统方法时,这种现象先前已经被检测到,因此它可能是计算中固有的。虽然统计波动的影响可以通过外推过程来消除,但由于有限的箱大小而导致的离散化误差更难以表征。通过正确选择箱的大小,可以在任何状态下,甚至接近凝固点,实现对三粒子熵贡献的良好估计。我们观察到,尽管事实上,三粒子的贡献的幅度显着增加相比,两个粒子的贡献,接近冻结,由两个和三体项高估的过剩熵引起的误差超过了由近似的过剩熵与单独的两个体项引起的误差。

英文摘要:

We have computed the two and three-particle contribution to the entropy of a Weeks-Chandler-Andersen fluid via molecular dynamics simulations. The three-particle correlation function and entropy were computed with a new method which simplified calculation. Results are qualitatively similar to Lennard-Jones systems. We observed a numerical instability in the three-particle contribution. This phenomenon has been previously detected when the traditional method is used, thus it is likely to be intrinsic in the computation. While the effect of statistical fluctuations can be removed through an extrapolation procedure, the discretization error due to finite bin size is more difficult to characterize. With a correct choice of the bin size, a good estimate of the three-particle entropy contribution can be achieved at any state, even close to the freezing point. We observed that, despite the fact that the magnitude of the three-particle contribution increases significantly compared to the two-particle contribution as freezing is approached, the error induced from overestimation of the excess entropy by the two and three-body terms exceeds that induced by approximating the excess entropy with the two body term alone.

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