Calculation of viscosities of branched alkanes from 0.1 to 1000 MPa by molecular dynamics methods using COMPASS force field
Shear viscosity is one of the key subjects of molecular modeling studies since this quality is used in the development of lubricants. In this paper, we use molecular dynamics methods to predict viscosity dependence on pressure up to 1000 MPa for 2,2,4-trimethylhexane. The COMPASS class II force field is used to determine atomic interactions in the model. The shear viscosity is calculated using Green-Kubo and Müller-Plathe methods. To achieve the convergence of the Green-Kubo integral, the time decomposition method is used. The approach is validated by 2,2,4-trimethylpentane for which experimental data are available. The calculated 2,2,4-trimethylhexane viscosity coefficient dependence is fit by Tait-like equation and does not show super-Arrhenius behavior. The Tait fit matches the experiment produced by Scott Bair for the pressures up to 500 MPa within the accuracy of the methods.