Physically Motivated, Robust, ab Initio Force Fields for CO2 and N2

We present a novel methodology for developing physically motivated, first-principles polarizable force fields and apply these techniques to the specific cases of CO2 and N-2. Exchange, electrostatic, induction, and dispersion interaction parameters were fit to symmetry adapted perturbation theory (SAPT) dimer energy calculations, with explicit terms to account for each of the dominant fundamental interactions between molecules. Each term is represented by a physically appropriate functional form and fitted individually based on the results of the SAPT decomposition. The resulting CO2 and N-2 force field was benchmarked against a diverse set of experimental data, including the second virial coefficient, density, scattering structure factor, heat capacity, enthalpy of vaporization, and vapor liquid coexistence curves. In general, excellent agreement with experimental data is obtained with our model. Due to the physical nature of their construction, these force fields are robust and transferable to environments for which they were not specifically parametrized, including gas mixtures, and we anticipate applications in modeling CO2/N-2 adsorption in polar and/or heterogeneous media.