Daidone Isabella, Foffi Riccardo, Amadei Andrea, Zanetti-Polzi Laura
Department of Physical and Chemical Sciences, University of L'Aquila, via Vetoio (Coppito 1), L'Aquila 67010, Italy.
Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Laura-Hezner-Weg 7, 8093 Zürich, Switzerland.
J Chem Phys. 2023 Sep 7;159(9). doi: 10.1063/5.0157505.
In this paper, we apply a theoretical model for fluid state thermodynamics to investigate simulated water in supercooled conditions. This model, which we recently proposed and applied to sub- and super-critical fluid water [Zanetti-Polzi et al., J. Chem. Phys. 156(4), 44506 (2022)], is based on a combination of the moment-generating functions of the enthalpy and volume fluctuations as provided by two gamma distributions and provides the free energy of the system as well as other relevant thermodynamic quantities. The application we make here provides a thermodynamic description of supercooled water fully consistent with that expected by crossing the liquid-liquid Widom line, indicating the presence of two distinct liquid states. In particular, the present model accurately reproduces the Widom line temperatures estimated with other two-state models and well describes the heat capacity anomalies. Differently from previous models, according to our description, a cluster of molecules that extends beyond the first hydration shell is necessary to discriminate between the statistical fluctuation regimes typical of the two liquid states.
在本文中，我们应用一种流体状态热力学理论模型来研究过冷条件下的模拟水。该模型是我们最近提出并应用于亚临界和超临界流体水的[扎内蒂 - 波尔齐等人，《化学物理杂志》156(4)，44506(2022)]，它基于由两个伽马分布提供的焓和体积涨落的矩生成函数的组合，并提供系统的自由能以及其他相关热力学量。我们在此处的应用给出了与通过液 - 液维德曼线所预期的完全一致的过冷水的热力学描述，表明存在两种不同的液态。特别地，本模型准确地再现了用其他两态模型估计的维德曼线温度，并很好地描述了热容异常。与先前的模型不同，根据我们的描述，区分两种液态典型的统计涨落区域需要一群延伸到第一水合层之外的分子。
