First Principles Monte Carlo Simulations of Vapor-Liquid Equilibria: Investigation of Dispersion-Corrected Functionals

Gibbs ensemble Monte Carlo simulations are used to compute the vapor-liquid phase equilibria for water, methanol, and methane using Kohn-Sham density functional theory.  The effects of various dispersion corrections for common generalized gradient approximation functional are investigated.  These dispersion corrections lead to much improved accuracy for the vapor-liquid coexistence curves of methanol and methane, but the situation is less promising for water.  It appears that improved dispersion corrections will be required to increase the fidely of first principles simulations for molecular systems.