Equilibrium Phase Dome and Critical Point of 1-Pentanol From Two-Phase Molecular Dynamics Simulations: Transferability of An Ab-Initio Pair-Potential Model

All-atom, site-site pair-potential parameters fitted solely from ab-initio landscapes for small alcohol dimers are used in two-phase Molecular Dynamics simulations to determine coexisting liquid and vapor densities of 1-pentanol as a function of temperature.  A Monte Carlo (MC) sampling method is used to extract the bulk vapor and liquid densities from the two-phase MD simulations and the critical point is determined from the resultant equilibrium densities in conjunction with the law of rectilinear diameters and the known critical exponent for the liquid-vapor density difference. Results obtained for the critical temperature, the critical density, and bulk vapor and liquid densities for the model are compared to experimental data. Errors due to transferability of the potential model are separated from errors due to the use of a true-pair potential by calculating energy landscapes for dimers of 1-pentanol using counterpoise (CP) corrected energies at the MP2/6-311 + G(2df,2pd) level and comparing these to the transferred potential models. The calculated landscapes were sampled at ten dimer separation distances for four different routes or relative orientations of the rigid monomers.