Thermostats and thermostat strategies for molecular dynamics simulations of nanofluidics

Abstract

The thermostats in molecular dynamics (MD) simulations of highly confined channel flow may have significant influences on the fidelity of transport phenomena. In this study, we exploit non-equilibrium MD simulations to generate Couette flows with different combinations of thermostat algorithms and strategies. We provide a comprehensive analysis on the effectiveness of three thermostat algorithms Nosé-Hoover chain (NHC), Langevin (LGV) and dissipative particle dynamics (DPD) when applied in three thermostat strategies, thermostating either walls (TW) or fluid (TF), and thermostating both the wall and fluid (TWTF). Our results of thermal and mechanical properties show that the TW strategy more closely resembles experimental conditions. The TF and TWTF systems also produce considerably similar behaviors in weakly sheared systems, but deviate the dynamics in strongly sheared systems due to the isothermal condition. The LGV and DPD thermostats used in the TF and TWTF systems provide vital ways to yield correct dynamics in coarse-grained systems by tuning the fluid transport coefficients. Using conventional NHC thermostat to thermostat fluid only produces correct thermal behaviors in weakly sheared systems, and breaks down due to significant thermal inhomogeneity in strongly sheared systems.

Water diffusion in zeolite membranes: Molecular dynamics studies on effects of water loading and thermostat

“…keeping the walls rigid), has a significant effect on properties of fluids undergoing Couette flow [31]. Yong and Zhang [32] 5 extended this work, comparing the effects of LGV, dissipative particle dynamics (DPD) and simulations with NH chain thermostats on Couette flow of Lennard-Jones particles, thermostatting walls and/or fluid and found that thermostatting the walls gave better agreement with experiments. A recent work on the diffusion rates of water through carbon nanotubes subject to pressure gradients showed discrepancies in the results obtained using different thermostatting methods [33].…”

Advances in nonequilibrium molecular dynamics simulations of lubricants and additives

“…For confined NEMD simulations, alternative thermostatting strategies are required; Yong and Zhang [54] evaluated some of these in 2013. In confined NEMD simulations, the thermostat is usually only applied to the wall atoms [54], allowing a thermal gradient to develop through the thickness of the lubricant film, as occurs in real experiments [55].…”

“…In confined NEMD simulations, the thermostat is usually only applied to the wall atoms [54], allowing a thermal gradient to develop through the thickness of the lubricant film, as occurs in real experiments [55]. The 6 Friction | https://mc03.manuscriptcentral.com/friction localised thermostat is often only applied in the Cartesian directions perpendicular to the shearing direction in order to avoid significantly affecting the dynamics.…”

Non-equilibrium phase behavior and friction of confined molecular films under shear: A non-equilibrium molecular dynamics study

“…[51][52][53] Thermostatting the wall atoms rather than the confined sample is the most physically realistic option. The implementation of bulk system thermostats without modification may lead to spurious particle dynamics.…”