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DY: Fachverband Dynamik und Statistische Physik

DY 36: Focus Session: Water – from Atmosphere to Space V (joint session CPP/DY)

DY 36.3: Vortrag

Mittwoch, 11. März 2026, 11:30–11:45, ZEU/0260

Liquid-vapor critical behavior of the TIP4P/2005 water model: Effects of NaCl solutes and hydrophobic confinement — •Mayank Sharma and Peter Virnau — Institute of Physics, Johannes Gutenberg University Mainz, 55128 Mainz, Germany

The liquid-vapor critical behavior of water is strongly influenced by both ionic solutes and confinement. Molecular dynamics simulations of aqueous NaCl solutions using the TIP4P/2005 water model and the Madrid-2019 ion parameters reveal a systematic increase in the liquid-vapor critical temperature and pressure with salt concentration, consistent with experimental trends. In contrast, confinement between parallel hydrophobic plates leads to a depression of the critical point. The critical temperature was determined using the Binder cumulant crossing in the NVT ensemble, based on a recently developed method originally applied to an active Brownian particle system [1]. The reliability of this approach was verified through complementary NPT simulations using histogram reweighting. We further demonstrate the pronounced sensitivity of the estimated critical point to the van der Waals cutoff distance, underscoring the importance of properly accounting for long-range interactions. The present results capture qualitative shifts in the critical point of water arising from ionic interactions and confinement, and the Binder-cumulant framework used here is readily extendable to other critical phenomena, including the putative liquid-liquid critical point of water.

[1] J.T Siebert et al., Phys. Rev. E 98, 030601 (2018).

Keywords: Molecular dynamics; Ionic solutions; Histogram reweighting; Binder cumulant; Finite-size scaling