A revisit of the density gradient theory and the mean field theory for the vaporliquid interface system
Abstract
In this work we define a meanfield crossover generated by the Maxwell construction as the dividing interface for the vaporliquid interface area. A highly accurate densityprofile equation is thus derived, which is physically favorable and leads to reliable predictions of interfacial properties. By using the density gradient theory and a meanfield equation of sate for the LennardJones fluid, we are able to extensively explore the interface system in terms of the Gibbs free energy, the Helmholtz free energy and heat capacity. The results show that the meanfield dividing interface is the natural extension of the Widom line into the coexistence region. Hence the entire phase space is coherently divided into liquidlike and gaslike regions in all three (temperaturepressurevolume) planes. Some unconventional behaviors are observed for the intrinsic heat capacity, being positive in low temperature region while negative in high temperature region. Finally, a complete picture of the meanfield equation of state is unfolded: all three solutions to a vaporliquid equilibrium problem have their respective significances.
 Publication:

arXiv eprints
 Pub Date:
 October 2021
 DOI:
 10.48550/arXiv.2110.07838
 arXiv:
 arXiv:2110.07838
 Bibcode:
 2021arXiv211007838L
 Keywords:

 Condensed Matter  Soft Condensed Matter;
 Condensed Matter  Statistical Mechanics;
 Physics  Chemical Physics
 EPrint:
 23 pages