Transport coefficients of liquid butane near the boiling point by equilibrium molecular dynamics

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Abstract
We present very precise results for the linear viscosity, thermal conductivity, and self-diffusion coefficient of the Ryckaert–Bellemans model of liquid butane near the boiling point, calculated from their respective Green–Kubo formulas using equilibrium molecular dynamics simulations. These results are used as a basis for the appraisal of previous calculations of these transport coefficients, which vary considerably. We find excellent agreement between our results and the results of the most precise nonequilibrium molecular dynamics simulations. We directly examine the system-size dependence of these transport coefficients for system sizes between 64 and 864 molecules and find that it is negligible, within experimental errors, for the viscosity and the thermal conductivity. The self-diffusion coefficient increases with increasing system size. The long-time decay of the shear stress, heat flux, and velocity autocorrelation function is also discussed quantitatively.