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arXiv 0807.0551cond-mat.softcond-mat.stat-mech
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液体中的压力-能量相关性。II。分析和后果

Pressure-energy correlations in liquids. II. Analysis and consequences

Nicholas P. Bailey, Ulf R. Pedersen, Nicoletta Gnan, Thomas B. Schrøder, Jeppe C. Dyre

摘要:

我们提出了一个分析,并讨论了强相关性的压力和能量的配置部分在其平衡波动在固定的体积报告的几种液体的模拟在配套文件[arXiv:0807.0550]的后果。分析集中在单组分Lennard-Jones系统。我们表明,潜在的可能被取代,在固定的体积,由一个有效的幂律,但不是因为只有短距离的遭遇占主导地位的波动。事实上,对波动的贡献与RDF的整个第一个峰值有关,正如我们通过分析空间分辨协方差矩阵所证明的那样。有效幂律定律之所以如此有效,取决于超越单对效应和固定体积的约束。特别是,一个更好的近似势包括一个线性项,这有助于势能和维里的平均值,但不是他们的波动。我们还研究了结晶相的T=0极限,其中相关系数变得非常接近,但不等于1。然后,我们考虑了强压力-能量相关性的四个结果:(1)分析超临界Ar的实验数据,我们发现96%的相关性;(2)我们讨论了接近玻璃化转变的粘性范德华液体的相关性所获得的意义:对于强相关的粘性液体,仅知道八个频率相关的热粘弹性响应函数中的一个基本上意味着知道所有这些函数;(3)重新解释了Mossa { \it et al.}在2002年,表明他们的结论遵循强相关性质;(4)我们讨论了模型生物膜中的相关性。

英文摘要:

We present an analysis and discuss consequences of the strong correlations of the configurational parts of pressure and energy in their equilibrium fluctuations at fixed volume reported for simulations of several liquids in the companion paper [arXiv:0807.0550]. The analysis concentrates specifically on the single-component Lennard-Jones system. We demonstrate that the potential may be replaced, at fixed volume, by an effective power-law, but not because only short distance encounters dominate the fluctuations. Indeed, contributions to the fluctuations are associated with the whole first peak of the RDF, as we demonstrate by an analysis of the spatially resolved covariance matrix. The reason the effective power-law works so well depends on going beyond single-pair effects and on the constraint of fixed volume. In particular, a better approximation to the potential includes a linear term, which contributes to the mean values of potential energy and virial, but not to their fluctuations. We also study the T=0 limit of the crystalline phase, where the correlation coefficient becomes very close, but not equal, to unity. We then consider four consequences of strong pressure-energy correlations: (1) analyzing experimental data for supercritical Ar we find 96% correlation; (2) we discuss the significance acquired by the correlations for viscous van der Waals liquids approaching the glass transition: For strongly correlating viscous liquids knowledge of just one of the eight frequency-dependent thermoviscoelastic response functions basically implies knowledge of them all; (3) we re-interpret aging simulations of ortho-terphenyl carried out by Mossa {\it et al.} in 2002, showing their conclusions follow from the strongly correlating property; and (4) we discuss correlations in model biomembranes.

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