Guiselin Benjamin, Tarjus Gilles, Berthier Ludovic
Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, 34095 Montpellier, France.
LPTMC, CNRS-UMR 7600, Sorbonne Université, 4 Pl. Jussieu, 75252 Paris Cedex 05, France.
J Chem Phys. 2020 Dec 14;153(22):224502. doi: 10.1063/5.0022614.
The overlap, or similarity, between liquid configurations is at the core of the mean-field description of the glass transition and remains a useful concept when studying three-dimensional glass-forming liquids. In liquids, however, the overlap involves a tolerance, typically of a fraction a/σ of the inter-particle distance, associated with how precisely similar two configurations must be for belonging to the same physically relevant "state." Here, we systematically investigate the dependence of the overlap fluctuations and of the resulting phase diagram when the tolerance is varied over a large range. We show that while the location of the dynamical and thermodynamic glass transitions (if present) is independent of a/σ, that of the critical point associated with a transition between a low- and a high-overlap phase in the presence of an applied source nontrivially depends on the value of a/σ. We rationalize our findings by using liquid-state theory and the hypernetted-chain approximation for correlation functions. In addition, we confirm the theoretical trends by studying a three-dimensional glass-former by computer simulations. We show, in particular, that a range of a/σ below what is commonly considered maximizes the temperature of the critical point, pushing it up in a liquid region where viscosity is low and computer investigations are easier due to a significantly faster equilibration.
液体构型之间的重叠或相似性是玻璃化转变平均场描述的核心，并且在研究三维玻璃形成液体时仍然是一个有用的概念。然而，在液体中，这种重叠涉及一个容差，通常为粒子间距离的分数a/σ，它与两种构型必须多么精确地相似才能属于同一物理相关“状态”有关。在这里，我们系统地研究了容差在大范围变化时重叠涨落以及由此产生的相图的依赖性。我们表明，虽然动力学和热力学玻璃化转变（如果存在）的位置与a/σ无关，但在存在外加源的情况下，与低重叠相和高重叠相之间转变相关的临界点的位置却非平凡地依赖于a/σ的值。我们通过使用液态理论和关联函数的超网链近似来解释我们的发现。此外，我们通过计算机模拟研究一种三维玻璃形成体来证实理论趋势。特别是，我们表明，一系列低于通常认为的a/σ值能使临界点的温度最大化，将其推到一个液体区域，在该区域粘度低，并且由于平衡速度显著加快，计算机研究更容易进行。
