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The technical development of supercritical CO 2 , energy systems, CO 2  capture, and other applications has become a hot topic in recent years. Therefore, molecular dynamics simulation (MD) of CO 2 , especially the investigation at the CO 2  supercritical region is urgently needed. This study focused on the optimization of common CO 2  potential model EPM2 (elementary physical model—2) combined MD forcefield OPLS-AA (optimized potentials for liquid simulations—all atom) and CHARMM (chemistry at Harvard macromolecular mechanics for MD simulation). Through adjusting angle parameters according to EPM2, vapor-liquid equilibrium curve, critical point and supercritical region could be well corresponding with experiments, which can be more accurate than previous approaches. The simulated results using 179.63° in OPLS-AA forcefield can not only correspond to supercritical phase of near-critical region (within ±10% error range under CO 2  is at 468 kg/m 3 , 304.2–320 K, 7.2–10.0 MPa), but also be consistent with actual CO 2  properties in gas phase of near-critical region (temperature range can reach 304.2–350 K while the density scope can reach 15–168 kg/m 3 ). Besides, optimized potential model also has a certain reliability on the investigation of CO 2  diffusion properties. The values simulated have the same order of magnitude as literature values, especially simulated diffusion coefficient values at gas phase. The CO 2  property of heat capacity is also simulated, and the errors are within ±15%. That is to say, the optimized CO 2  potential parameter also has a certain accuracy to analyze CO 2  heat transfer. The angle value optimized in this study may be useful for the fundamental understanding of the supercritical state and it can well be applied in the further investigation of CO 2  systems.

Molecular Dynamics Study of CO 2 Phase Change Transport in the Near-Critical Region: Model Parameter Optimization