Thermodynamics of Fluid Polyamorphism
Thermodynamics of Fluid Polyamorphism
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DOI：
10.1103/physrevx.8.011004
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发表时间：
2018-01-10
影响因子：
12.5
通讯作者：
Sadus, Richard J.
中科院分区：
文献类型：
--
作者：
Anisimov, Mikhail A.;Duska, Michal;Sadus, Richard J.
流体多晶化是指单一组分流体中存在不同的凝聚无定形状态。通常在极端条件下，人们发现或预测了一大类非常不同的物质，包括氦、碳、硅、磷、硫、碲、铈、氢和四碘化锡。这种现象也适用于亚稳态和深度过冷的水，据推测，这些水比均质冰形成的实验极限低几度。我们提出了一种通用的唯象方法来描述单组分流体中的多晶化，它完全独立于该现象的分子起源。我们发现，流体多晶化可以在有或没有流体相分离的情况下发生，这取决于序参数的对称性。在后一种情况下，它与二级转变有关，例如在液氦或液态硫中。为了说明现象学，我们考虑在两个不同的可相互转化的状态或分子结构之间具有热力学平衡的流体。这一概念的一个基本标志是确定每一种可选状态所涉及的分子的平衡分数。然而，只有当这些结构的混合不理想时，替代结构的存在才可能导致多相流体相分离。两态热力学统一了凝聚态物理不同领域中所有关于流体多晶化的争论场景，无论有没有相分离，甚至超越了多晶化现象，概括地描述了表现出交替分子状态相互转化的流体的反常性质。
Fluid polyamorphism is the existence of different condensed amorphous states in a single-component fluid. It is either found or predicted, usually at extreme conditions, for a broad group of very different substances, including helium, carbon, silicon, phosphorous, sulfur, tellurium, cerium, hydrogen, and tin tetraiodide. This phenomenon is also hypothesized for metastable and deeply supercooled water, presumably located a few degrees below the experimental limit of homogeneous ice formation. We present a generic phenomenological approach to describe polyamorphism in a single-component fluid, which is completely independent of the molecular origin of the phenomenon. We show that fluid polyamorphism may occur either in the presence or in the absence of fluid phase separation depending on the symmetry of the order parameter. In the latter case, it is associated with a second-order transition, such as in liquid helium or liquid sulfur. To specify the phenomenology, we consider a fluid with thermodynamic equilibrium between two distinct interconvertible states or molecular structures. A fundamental signature of this concept is the identification of the equilibrium fraction of molecules involved in each of these alternative states. However, the existence of the alternative structures may result in polyamorphic fluid phase separation only if mixing of these structures is not ideal. The two-state thermodynamics unifies all the debated scenarios of fluid polyamorphism in different areas of condensed-matter physics, with or without phase separation, and even goes beyond the phenomenon of polyamorphism by generically describing the anomalous properties of fluids exhibiting interconversion of alternative molecular states.