近日，美国加州理工学院的John F.Brady研究小组与宾夕法尼亚州立大学的Stewart A.Mallory等人合作，提出了非平衡共存和运动诱导相分离的机械理论。相关研究成果已于2023年4月24日在国际知名学术期刊《美国科学院院刊》上发表。
该研究团队提出了一种基于半个世纪前研究不均匀流体的思想的相分离通用机械理论。该理论的核心思想是，在分离两个共存相的界面内的机械力唯一地确定了共存准则，无论系统是否处于平衡状态。通过将该理论应用于活性布朗粒子，研究人员预测了二维和三维运动诱导相分离的定量相图，展示了该理论的能力和实用性。
此外，这种理论还允许预测新的界面现象，例如在深入两相区域时界面宽度的增加，这是计算机模拟证实的独特非平衡效应。该机械视角提供了关于体相行为和界面现象的自洽测定，为非平衡相变的普遍理论提供了具体的发展方向。
据悉，非平衡相变在自然和人造系统中经常被观察到，这凸显了一个明显的缺陷，即缺乏一种普遍适用于非平衡和平衡系统的相共存理论。
附：英文原文
Title: Mechanical theory of nonequilibrium coexistence and motility-induced phase separation
Author: Omar, Ahmad K., Row, Hyeongjoo, Mallory, Stewart A., Brady, John F.
Issue&Volume: 2023-4-24
Abstract: Nonequilibrium phase transitions are routinely observed in both natural and synthetic systems. The ubiquity of these transitions highlights the conspicuous absence of a general theory of phase coexistence that is broadly applicable to both nonequilibrium and equilibrium systems. Here, we present a general mechanical theory for phase separation rooted in ideas explored nearly a half-century ago in the study of inhomogeneous fluids. The core idea is that the mechanical forces within the interface separating two coexisting phases uniquely determine coexistence criteria, regardless of whether a system is in equilibrium or not. We demonstrate the power and utility of this theory by applying it to active Brownian particles, predicting a quantitative phase diagram for motility-induced phase separation in both two and three dimensions. This formulation additionally allows for the prediction of novel interfacial phenomena, such as an increasing interface width while moving deeper into the two-phase region, a uniquely nonequilibrium effect confirmed by computer simulations. The self-consistent determination of bulk phase behavior and interfacial phenomena offered by this mechanical perspective provide a concrete path forward toward a general theory for nonequilibrium phase transitions.
DOI: 10.1073/pnas.2219900120
Source: https://www.pnas.org/doi/10.1073/pnas.2219900120
来源：科学网 小柯机器人