发表机构
UT-Battelle, LLC（UT-Battell有限责任公司）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过分子动力学模拟发现，大积分时间步长会人为增强疏水相互作用，其机制在于疏水贡献的变化，而亲水贡献不受影响。
AI 中文摘要
分子动力学模拟被用于计算两个联合原子甲烷分子在多个温度和积分时间步长下的平均力势（PMF）。在固定的时间步长下，PMF的接触最小值随温度升高而加深，这符合疏水驱动的缔合预期。与0.5飞秒（该步长保持能量均分）的时间步长相比，较大的时间步长改变了PMF并使接触最小值更为有利。因此，即使是相对自由能值也对破坏能量均分的时间步长敏感。利用准化学理论，我们将缔合自由能分解为疏水和亲水贡献。亲水贡献反对缔合，且对时间步长不敏感。因此，在较大时间步长下缔合的人为增强完全来自疏水贡献。我们通过液体内压的温度依赖性来解释这一行为。同样的分析也解释了早期在破坏能量均分条件下观察到的液体p-V行为。
英文摘要
Molecular dynamics simulations are used to compute the potential of mean force (PMF) between two united-atom methane molecules at several temperatures and integration time-steps. At a fixed time-step, the contact minimum of the PMF deepens with increasing temperature, as expected for hydrophobicity driven association. Compared with a time-step of 0.5 fs, one that preserves equipartition, larger time-steps alter the PMF and make the contact minimum more favorable. Thus even relative free energy values are sensitive to time-steps that break equipartition. Using quasichemical theory, we partition the free energy of association into hydrophobic and hydrophilic contributions. The hydrophilic contribution opposes association and is insensitive to the time-step. Thus the artificial enhancement of association at larger time-steps comes entirely from the hydrophobic contribution. We explain this behavior through the temperature dependence of the internal pressure of the liquid. The same analysis also accounts for earlier observations of the liquid's p-V behavior under conditions that break equipartition.
