Parametric dependence on shear viscosity of SPC/E water from equilibrium and non-equilibrium molecular dynamics simulations

Abstract

A parametric dependent study is crucial for the accurate determination of transport coefficients such as shear viscosity. In this study, we calculate the shear viscosity of extended simple point charge water using a transverse current auto-correlation function (TCAF) from equilibrium molecular dynamics (EMD) and the periodic perturbation method from non-equilibrium molecular dynamics (NEMD) simulations for varying coupling time and system sizes. Results show that the shear viscosity calculated using EMD simulations with different thermostats varies significantly with coupling times and system size. The use of Berendsen and velocity-rescale thermostats in NEMD simulations generates a significant drift from the target temperature and results in an inconsistent shear viscosity with coupling time and system size. The use of Nosé–Hoover thermostat in NEMD simulations offers thermodynamic stability which results in a consistent shear viscosity for various coupling times and system sizes.

Keywords::

• molecular dynamics
• shear viscosity
• transverse current auto-correlation
• periodic perturbation
• coupling time

Acknowledgements

This study used the computing resources provided by Indian Institute of Science Education and Research, Pune. Anurag thanks the University Grants Commission for Senior Research Fellowship. The authors thank Department of Science and Technology, India (SR/S1/PC/28/2009) and Department of Science and Technology, Nanomission (SR/NM/NS-42/2009) for generous financial support.

Notes

^1. See Figure S1 of Supplementary Material (online only) for k-dependent shear viscosity calculated using the transverse current auto-correlation method.