Vapor–Liquid Interfacial Properties of CO 2 Mixtures for Sequestration Applications: Molecular Simulations, Classical Density Functional Theory, and Equations of State

Experimentally determining interfacial tension (IFT) for compositions relevant to CO 2 transport is challenging. We address this using molecular dynamics (MD) simulations and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state with classical density functional theory. We compute phase equilibria and interfacial properties of pure CO 2 and CO 2 –CH 4, CO 2 –Ar, CO 2 –N 2, and CO 2 –H 2 mixtures at 220–273 K. Both approaches accurately estimate CO 2 phase equilibria and IFTs. For binary mixtures, phase equilibria computed using PC-SAFT agree well with experiments when k ij ≠ 0. IFTs computed from PC-SAFT depend strongly on k ij, while MD simulations systematically overpredict IFTs. The IFT decreases with increasing pressure, least pronouncedly for H 2 -containing mixtures. Binary mixtures exhibit interfacial enrichment of the light boiling component, decreasing with increasing temperature and pressure. Semiempirical Parachor and Winterfeld–Scriven–Davis models capture IFT–pressure trends with mixture-dependent accuracy. These results improve predictions of metastable limits and provide key insights for fast-transient multiphase CO 2 flow modeling.