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arXiv 2012.06451physics.plasm-ph
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径向对势近似在稠密等离子体分子动力学模拟中的有效性

Efficacy of the Radial Pair Potential Approximation for Molecular Dynamics Simulations of Dense Plasmas

Lucas J. Stanek, Raymond C. Clay, M. W. C. Dharma-wardana, Mitchell A. Wood, Kristian R. C. Beckwith, Michael S. Murillo

摘要:

稠密等离子体的宏观模拟依赖于详细的微观信息,这些信息在计算上可能是昂贵的,并且难以通过实验验证。在这项工作中,我们描绘了微观模拟方法之间的准确性边界比较科恩-沙姆密度泛函理论分子动力学(KS-MD)和径向对势分子动力学(RPP- MD)的一系列元素,温度和密度。通过使用力匹配从KS-MD数据中提取最佳RPP,我们约束其函数形式并驳回假定小粒子间距离的恒定幂律的潜在类别。我们的研究结果表明,RPP-MD和KS-MD之间的多个指标的准确性,在温度只有几个电子伏特的良好协议。RPP的使用提供了几个数量级的计算成本的降低,并表明,三体势是不需要超过几个电子伏特的温度。由于其效率,经验证的RPP-MD提供了一种减少由于有限尺寸效应(可能为$\sim20\%$量级)而导致的误差的途径。

英文摘要:

Macroscopic simulations of dense plasmas rely on detailed microscopic information that can be computationally expensive and is difficult to verify experimentally. In this work, we delineate the accuracy boundary between microscale simulation methods by comparing Kohn-Sham density functional theory molecular dynamics (KS-MD) and radial pair potential molecular dynamics (RPP- MD) for a range of elements, temperature, and density. By extracting the optimal RPP from KS-MD data using force-matching, we constrain its functional form and dismiss classes of potentials that assume a constant power law for small interparticle distances. Our results show excellent agreement between RPP-MD and KS-MD for multiple metrics of accuracy at temperatures of only a few electron volts. The use of RPPs offers orders of magnitude decrease in computational cost and indicates that three-body potentials are not required beyond temperatures of a few eV. Due to its efficiency, the validated RPP-MD provides an avenue for reducing errors due to finite-size effects that can be on the order of $\sim20\%$.

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