Phase Equilibria and Condensed Phase Properties of Fluorinated Alkanes via First Principles Simulations

摘要

abstract_textpVapor liquid equilibria (VLE) of organic compounds is governed by weak non-covalent interactions. This presents a significant challenge in predicting VLE using a first principles approach where density functional theory is used to model system potential. However, a dispersion corrected approach has significantly improved the performance of traditional density functionals. Here, we predict the VLE for a nonpolar carbon tetrafluoride (R14) and polar 1,1,1,2-tetrafluoroethane (R134a) via first principles Gibbs ensemble Monte Carlo simulations using PBE-D3 density functional. We find that the saturated liquid density for R14 is slightly under predicted for subcritical temperatures, while for R134a it is under predicted at lower reduced temperatures and over predicted at higher reduced temperatures. In the liquid phase, angle-resolved pair correlation functions indicate slight preference for R143a to align in parallel and antiparallel orientation in the first solvation shell. The vibrational spectra reveal peak broadening in the condensed phase due to solvothermal effects. Overall, we find the PBE-D3 functional performance is better for the nonpolar molecule as compared to the polar one./p/abstract_text