Transferable force field for equilibrium and transport properties in linear, branched, and bifunctional amines I....

A new anisotropic united atom (AUA4) force field is developed to predict the phase equilibrium and transport properties of different primary amines. The force field transferability was studied for an important set of molecules, including linear amines (methyl, ethyl, n-propyl, and n-hexylamine), branched amines (isopropyl and isobutylamine), and bifunctional amines (ethylenediamine, 1,3-propanediamine, and 1,5-pentanediamine). Monte Carlo simulations in the Gibbs ensemble were carried out to study thermodynamic properties such as equilibrium densities, vaporization enthalpies, and vapor pressures. Critical coordinates (critical density, critical temperature, and critical pressure) and normal boiling points were also calculated. The shear viscosity coefficients were studied for methyl, ethyl, and n-propylamine at different temperatures using molecular dynamics. Our results show a very good agreement with experimental values for thermodynamic properties and are an improvement on the models available in the literature, all of which are all-atom. Viscosity coefficients also show a good agreement compared with experimental data, demonstrating the transferability of our force field not only to predict thermodynamic properties but also to predict transport properties.