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arXiv 2301.00465cond-mat.soft
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粗粒化流体的相行为

Phase behaviour of coarse-grained fluids

Vlad P Sokhan, Michael A Seaton, Ilian T Todorov

AI总结:

本文研究一种含有限程吸引的软粗粒化模型的完整相图,揭示其与Lennard-Jones势定性不同的多种热力学异常,为理解简单势模型与复杂凝聚态现象的联系提供新见解。

摘要:

软凝聚态结构常常以受集体模式支配的复杂多体现象向我们提出挑战,这些集体模式跨越宽广的空间和时间域。为了成功解决此类问题,介观粗粒化(CG)统计模型正在发展之中,从而大幅降低计算复杂度。CG模型在连接凝聚相热力学与其组成原子和分子性质的复杂统计框架中提供了一个中间步骤。这些模型使我们能够将部分问题转移给CG模型本身,并在约化的CG相空间中重新表述其余部分。然而,这种将兵卒换成棋子,即“哈密顿重正化”的做法,是一个激进的步骤,原始原子模型与CG模型的热力学可能存在显著差异。在此,我们对一种新型软CG模型的相图进行了全面研究,包括双节线和界面性质,该模型包含有限程吸引并支持液相。尽管该模型植根于与Lennard-Jones(LJ)原子对势类似的论证,但其相行为与LJ定性不同,并表现出若干异常,例如异常宽的液相范围、液相共存支随模型参数变化的凹性改变、熔化时的体积收缩、液相中的最大密度温度以及固相中的负热膨胀。这些结果为简单势模型与复杂涌现凝聚态现象之间的联系提供了新的见解。

英文摘要:

Soft condensed matter structures often challenge us with complex many-body phenomena governed by collective modes spanning wide spatial and temporal domains. In order to successfully tackle such problems mesoscopic coarse-grained (CG) statistical models are being developed, providing a dramatic reduction in computational complexity. CG models provide an intermediate step in the complex statistical framework of linking the thermodynamics of condensed phases with the properties of their constituent atoms and molecules. These allow us to offload part of the problem to the CG model itself and reformulate the remainder in terms of reduced CG phase space. However, such exchange of pawns to chess pieces, or ``Hamiltonian renormalization'', is a radical step and the thermodynamics of the primary atomic and CG models could be markedly different. Here, we present a comprehensive study of the phase diagram including binodal and interfacial properties of a novel soft CG model, which includes finite-range attraction and supports liquid phases. Although the model is rooted in similar arguments to the Lennard-Jones (LJ) atomic pair potential, its phase behaviour is qualitatively different from that of LJ and features several anomalies such as an unusually broad liquid range, change in concavity of the liquid coexistence branch with variation of the model parameters, volume contraction on fusion, temperature of maximum density in the liquid phase and negative thermal expansion in the solid phase. These results provide new insight into the connection between simple potential models and complex emergent condensed matter phenomena.

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