Determination of pressure-viscosity relation of 2,2,4-trimethylhexane by all-atom molecular dynamics simulations

Abstract

The Newtonian viscosity of 2,2,4-trimethylhexane at 293 K is determined at pressures from 0.1 MPa to 1000 MPa. Non-equilibrium molecular dynamics simulations are performed using AIREBO-M, an all-atom potential for hydrocarbons especially parameterized for high pressures. The steady-state shear stress and viscosity are determined from simple shear simulations at rates between 107 and 5⋅109s−1. At low pressures, simulation rates are low enough to reach the Newtonian regime. At high pressures, results are extrapolated to the Newtonian limit by fitting rate-dependent viscosities to Eyring theory. The variation of viscosity with pressure has an inflection point that is common for small molecules. Deviations from experiment are less than 40%.