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<p>By integrating the contribution of chain conformation into the free-energy functional of chain molecules, we present a density functional theory approach to describe phase equilibria and interfacial tensions of <i>n</i>-alkanes. In the theoretical approach, the force field parameters of <i>n</i>-alkanes are taken directly from the TraPPE united-atom model, and the number of chain segments is strictly equal to monomer number; thus, the presented results are strict predictions. During an equilibrium calculation, the transforms of chemical potential and pressure versus density are carried out by taking the effect of volume size into account, and the two singular points of phase transition are obtained. The phase coexistence curves and vaporization enthalpies of a series of <i>n</i>-alkanes (from ethane to <i>n</i>-decane, as well as <i>n</i>-dodecane) are computed. Besides, surface tensions are calculated based on the equilibrium density profiles of vapor–liquid interfaces. These predictions are examined by the corresponding experimental data, and the errors are acceptable in industrial applications.</p>

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Modeling of phase transitions and surface tensions of n-alkanes with consideration of chain conformation

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Di Zhou,
  • Yuxi Shi

摘要

By integrating the contribution of chain conformation into the free-energy functional of chain molecules, we present a density functional theory approach to describe phase equilibria and interfacial tensions of n-alkanes. In the theoretical approach, the force field parameters of n-alkanes are taken directly from the TraPPE united-atom model, and the number of chain segments is strictly equal to monomer number; thus, the presented results are strict predictions. During an equilibrium calculation, the transforms of chemical potential and pressure versus density are carried out by taking the effect of volume size into account, and the two singular points of phase transition are obtained. The phase coexistence curves and vaporization enthalpies of a series of n-alkanes (from ethane to n-decane, as well as n-dodecane) are computed. Besides, surface tensions are calculated based on the equilibrium density profiles of vapor–liquid interfaces. These predictions are examined by the corresponding experimental data, and the errors are acceptable in industrial applications.