The putative liquid-liquid transition is a liquid-solid transition in atomistic models of water. II
The putative liquid-liquid transition is a liquid-solid transition in atomistic models of water. II
复制标题
DOI：
10.1063/1.4807479
复制
发表时间：
2013-06-07
影响因子：
4.4
通讯作者：
Chandler, David
中科院分区：
文献类型：
--
作者：
Limmer, David T.;Chandler, David
本文扩展了我们早期对过冷水模型的密度和晶序参数的自由能函数的研究，使我们能够检验两种不同亚稳液相的可能性[D]。T. Limmer和D. Chandler， J. Chem。物理学报，135,134503(2011)，预印本arXiv:1107.0337（2011）。计算了几种不同原子模型的低温可逆自由能表面：mW水、TIP4P/2005水、Stillinger-Weber硅和ST2水，最后比较了三种不同的远程力处理。在每种情况下，我们都证明存在一个稳定或亚稳的液相，以及一个冰状的晶体相。这些体系结晶的时间尺度远远超过过冷亚稳液体中结构弛豫的时间尺度。我们展示了这种时间尺度上的广泛分离是如何产生低温液-液过渡的错觉的。提示两种不同液相亚稳态的现象实际上是有序的类冰相的粗化，我们用解析理论和计算机模拟来阐明这一点。对于后者，我们描述了计算可逆自由能表面的鲁棒方法，并考虑了静电边界条件的影响。我们表明，模型和边界条件的明显改变不会对这些系统的低温相行为产生质变，只有状态方程的边际变化。另一方面，我们表明改变采样时间尺度可以产生大的和定性的非平衡效应。最近报告的证据表明，在过冷水的计算机模拟中存在液-液临界点。(C) 2013 AIP出版有限责任公司
This paper extends our earlier studies of free energy functions of density and crystalline order parameters for models of supercooled water, which allows us to examine the possibility of two distinct metastable liquid phases [D. T. Limmer and D. Chandler, J. Chem. Phys. 135, 134503 (2011) and preprint arXiv:1107.0337 (2011)]. Low-temperature reversible free energy surfaces of several different atomistic models are computed: mW water, TIP4P/2005 water, Stillinger-Weber silicon, and ST2 water, the last of these comparing three different treatments of long-ranged forces. In each case, we show that there is one stable or metastable liquid phase, and there is an ice-like crystal phase. The time scales for crystallization in these systems far exceed those of structural relaxation in the supercooled metastable liquid. We show how this wide separation in time scales produces an illusion of a low-temperature liquid-liquid transition. The phenomenon suggesting metastability of two distinct liquid phases is actually coarsening of the ordered ice-like phase, which we elucidate using both analytical theory and computer simulation. For the latter, we describe robust methods for computing reversible free energy surfaces, and we consider effects of electrostatic boundary conditions. We show that sensible alterations of models and boundary conditions produce no qualitative changes in low-temperature phase behaviors of these systems, only marginal changes in equations of state. On the other hand, we show that altering sampling time scales can produce large and qualitative non-equilibrium effects. Recent reports of evidence of a liquid-liquid critical point in computer simulations of supercooled water are considered in this light. (C) 2013 AIP Publishing LLC.