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arXiv 2401.09355cond-mat.softphysics.chem-ph
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柔性水模型的势能景观:状态方程、构型熵与 Adam-Gibbs 关系

Potential Energy Landscape of a Flexible Water Model: Equation-of-State, Configurational Entropy, and Adam-Gibbs Relationship

Ali Eltareb, Gustavo E. Lopez, Nicolas Giovambattista

AI总结:

本文利用势能景观形式理论计算柔性 q-TIP4P/F 水模型的状态方程与构型熵,验证其液-液临界点及 Adam-Gibbs 关系,证明该方法可推广到含分子柔性的体系。

摘要:

势能景观(PEL)形式理论是统计力学中的一种工具,过去已被用于计算经典刚性模型液体在低温下的状态方程(EOS),而在该低温条件下计算机模拟可能具有挑战性。在本工作中,我们使用经典分子动力学(MD)模拟和 PEL 形式理论来计算柔性 q-TIP4P/F 水模型的 EOS。该模型在过冷区域表现出液-液临界点(LLCP),位于($P_c = 150$ MPa,$T_c = 190$ K,$ρ_c = 1.04$ g/cm$^3$)[使用反应场技术]。q-TIP4P/F 水的 PEL-EOS 以及相应的 LLCP 位置与 MD 模拟结果非常吻合。我们表明 q-TIP4P/F 水的 PEL 是高斯型的,这使我们能够计算系统的构型熵 $S_{conf}$。q-TIP4P/F 水的 $S_{conf}$ 与先前报道的刚性水模型的结果惊人地相似,这表明分子内柔性并不一定会增加 PEL 的粗糙度。我们还表明,将扩散系数 $D$ 与 $S_{conf}$ 联系起来的 Adam-Gibbs 关系对柔性 q-TIP4P/F 水模型成立。总体而言,我们的结果表明,PEL 形式理论可用于研究包含分子柔性的分子体系,而这是标准力场中的常见情况。这一点并非显然成立,因为在经典统计力学中引入大的弯曲/伸缩模式频率是有问题的。例如,如先前所示,我们发现这种高频会导致 q-TIP4P/F 水出现非物理的(负的)熵(然而 PEL 形式理论仍可成功应用)。

英文摘要:

The potential energy landscape (PEL) formalism is a tool within statistical mechanics that has been used in the past to calculate the equation of states (EOS) of classical rigid model liquids at low temperatures, where computer simulations may be challenging. In this work, we use classical molecular dynamics (MD) simulations and the PEL formalism to calculate the EOS of the flexible q-TIP4P/F water model. This model exhibits a liquid-liquid critical point (LLCP) in the supercooled regime, at ($P_c = 150$ MPa, $T_c = 190$ K, $ρ_c = 1.04$ g/cm$^3$) [using the reaction field technique]. The PEL-EOS of q-TIP4P/F water, and the corresponding location of the LLCP, are in very good agreement with the MD simulations. We show that the PEL of q-TIP4P/F water is Gaussian which allows us to calculate the configurational entropy of the system, $S_{conf}$. The $S_{conf}$ of q-TIP4P/F water is surprisingly similar to that reported previously for rigid water models, suggesting that intramolecular flexibility does not necessarily add roughness to the PEL. We also show that the Adam-Gibbs relation, which relates the diffusion coefficient $D$ with $S_{conf}$, holds for the flexible q-TIP4P/F water model. Overall, our results indicate that the PEL formalism can be used to study molecular systems that include molecular flexibility, the common case in standard force fields. This is not trivial since the introduction of large bending/stretching mode frequencies is problematic in classical statistical mechanics. For example, as shown previously, we find that such high-frequencies lead to an unphysical (negative) entropy for q-TIP4P/F water (yet the PEL formalism can be applied successfully).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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