arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1708.03573cond-mat.stat-mechphysics.chem-ph
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流体多形作用的热力学

Thermodynamics of Fluid Polyamorphism

Mikhail A. Anisimov, Michal Duška, Frédéric Caupin, Lauren E. Amrhein, Amanda Rosenbaum, Richard J. Sadus

摘要:

“流体多晶性”是指在单一组分流体中存在不同的凝聚非晶状态。通常在极端条件下,它被发现或预测为一组非常不同的物质,包括氦,碳,硅,磷,硫,碲,铈,氢和四碘化锡。这种现象也被假设为亚稳态和深度过冷水,大概位于均匀冰形成的实验极限以下几度。我们提出了一个通用的唯象方法来描述在单组分流体,这是完全独立的分子起源的现象多晶。我们表明,流体多形作用可能发生在存在或不存在流体相分离取决于对称性的序参量。在后一种情况下,它与二级跃迁有关,例如在液氦或液态硫中。为了说明现象学,我们考虑两个不同的相互转换状态或分子结构之间的热力学平衡的流体。这一概念的一个基本特征是识别参与这些替代状态中的每一个的分子的平衡分数。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晶流体相分离。双态热力学统一了凝聚态物理不同领域中关于流体多晶性的所有有争议的情景,包括有无相分离,甚至超越了多晶性现象,一般性地描述了表现出交替分子状态相互转化的流体的异常性质。

英文摘要:

"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 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.

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