Atomistic molecular dynamics simulations of H<sub>2</sub>O diffusivity in liquid and supercritical CO<sub>2</sub>

<div><p>Molecular dynamics simulations were employed for the calculation of diffusion coefficients of pure CO<sub>2</sub> and of H<sub>2</sub>O in CO<sub>2</sub> over a wide range of temperatures (298.15 K < <i>T</i> < 523.15 K) and pressures (5.0 MPa < <i>P</i> < 100.0 MPa), that are of interest to CO<sub>2</sub> capture-and-sequestration processes. Various combinations of existing fixed-point-charge force-fields for H<sub>2</sub>O (TIP4P/2005 and Exponential-6) and CO<sub>2</sub> (elementary physical model 2 [EPM2], transferable potentials for phase equilibria [TraPPE], and Exponential-6) were tested. All force-field combinations qualitatively reproduce the trends of the experimental data for infinitely diluted H<sub>2</sub>O in CO<sub>2</sub>; however, TIP4P/2005–EPM2, TIP4P/2005–TraPPE and Exponential-6–Exponential-6 were found to be the most consistent. Additionally, for H<sub>2</sub>O compositions ranging from infinite dilution to , the Maxwell–Stefan diffusion coefficient is shown to have a weak non-linear composition dependence.</p></div>