Leveraging local MP2 to reduce basis set superposition errors: An efficient first-principles based force-field for...

Pairwise additive model potentials for CO₂ were developed by fitting to gradients computed with the local second order Møller Plesset Perturbation theory (LMP2) method, with and without consideration of 3-body dispersion using adaptive force matching. Without fitting to experiments, all models gave good predictions of properties of CO₂, such as the density-temperature diagram, diffusion constants, and radial distribution functions. For the prediction of vibrational spectra, the inclusion of a bond-bond coupling term has been shown to be important. The CO₂ models developed only have pairwise additive terms, thus allowing microsecond time scale simulations to be performed with practical computational cost. LMP2 performed significantly better than second order Møller Plesset Perturbation theory (MP2) for the development of the CO₂ model. This is attributed to the appreciable reduction in the basis set superposition error when the localized method was used. It is argued that LMP2 is a more appropriate method than MP2 for force matching for systems where the basis set superposition error is large.