Monte Carlo Calculations for Alcohols and Their Mixtures with Alkanes. Transferable Potentials for Phase Equilibria. 5. United-Atom Description of Primary, Secondary, and Tertiary Alcohols

Abstract

The transferable potentials for phase equilibria-united atom (TraPPE-UA) force field for hydrocarbons is extended to primary, secondary, and tertiary alcohols by introducing the following (pseudo-)atoms: common hydroxyl O and H for all alcohols, α-CH3, α-CH2, α-CH, and α-C for methanol, primary, secondary, and tertiary alcohols, respectively. In the TraPPE-UA force field, the nonbonded interactions of these sites are governed by Lennard−Jones 12−6 potentials and Coulombic interactions of fixed partial charges. The values of these partial charges were borrowed from the optimized potentials for liquid simulations-united atom (OPLS−UA) force field [Jorgensen, W. L. J. Phys. Chem. 1986, 90, 1276]. The Lennard−Jones well depth and size parameters for the new interaction sites were determined by fitting to the single-component vapor−liquid-phase equilibria of a few selected model compounds. Although the well-depth parameters for the α-carbons could be taken directly from the TraPPE-UA parameters for the corres...