Statistics of small length scale density fluctuations in supercooled viscous liquids

UR Pedersen, JOURNAL OF CHEMICAL PHYSICS, 150, 094505 (2019).

DOI: 10.1063/1.5080277

Many successful theories of liquids near the melting temperature assume that small length scale density fluctuations follow Gaussian statistics. This paper presents a numerical investigation of density fluctuations in the supercooled viscous regime using an enhanced sampling method. Five model systems are investigated: the single component Lennard-Jones liquid, the Kob-Andersen binary mixture, the Wahnstrom binary mixture, the Lewis-Wahnstrom model of ortho-terphenyl, and the TIP4P/Ice model of water. The results show that the Gaussian approximation persists to a good degree into the supercooled viscous regime; however, it is less accurate at low temperatures. The analysis suggests that non-Gaussian fluctuations are related to crystalline configurations. Implications for theories of the glass transition are discussed. (C) 2019 Author(s).

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