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Updated: Jan 23, 2026

Protocol for Measuring the Thermal Properties of a Supercooled Synthetic Sand-water-gas-methane Hydrate Sample
Published on: March 21, 2016
Thermodynamic analysis of the stability of planar interfaces between coexisting phases and its application to
Rakesh S Singh1, Jeremy C Palmer2, Athanassios Z Panagiotopoulos1
1Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA.
Abstract:
Two-phase simulations are commonly used to evaluate coexistence conditions, interfacial tensions, and other thermodynamic properties associated with first-order phase transitions. Calculation of these properties is often simplified when the interfaces between the two phases are flat or planar. Here, we derive a general thermodynamic criterion for selecting simulation cell dimensions to stabilize planar interfaces in phase-separated fluid-fluid systems with respect to homogeneous, single-phase states. The resulting expression is validated by analyzing the effects of simulation cell dimensions on the formation of planar liquid-vapor interfaces in the Lennard-Jones fluid and in the TIP4P/2005 model of water. We also perform large scale molecular dynamics simulations to study metastable liquid-liquid phase separation in the ST2 and TIP4P/2005 models of water under deeply supercooled conditions. Our simulations confirm the stability of a liquid-liquid interface in ST2, and they demonstrate that the corresponding interface for TIP4P/2005 can be stabilized by judiciously choosing the simulation cell aspect ratio in a manner consistent with the thermodynamic criterion. We posit that this sensitivity to the simulation cell aspect ratio may explain discrepancies between previous studies examining liquid-liquid separation in models of supercooled water.
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