PMC

Flowchart of the machine learning with genetic algorithm (ML/GA) strategy describing the sequence of steps employed in this work.

Density (ρ) and heat of vaporization (ΔH_vap) of methanol as a function of temperature from MD simulations using the optimized polizable force field optimized from the DFMP2(fc)/jul-cc-pVDZ and DFMP2(fc)/jul-cc-pVTZ data. For comparison the results from experiments and the original AMOEBA force field (amoeba09.prm) are also shown.

Liquid structure of methanol. The radial distribution function of methanol determined from neutron scattering compares favorably with the present force field model. The O-H hydrogen bonding peak is, however, higher than the experiment. This may reflect the neglect of quantum effects of the nuclei in the simulations, as well as inaccuracies in the experimentally determined pair correlation functions.

Comparison of the interaction energy (_ΔE) for 1,250 methanol clusters, including 999 clusters of 9 molecules, 157 clusters of 11 molecules, and 94 clusters of 13 molecules, computed from (a) MP2/6-31G(d,p) (b) DFMP2(fc)/jul-cc-pVDZ, and (c) DFMP2(fc)/jul-cc-pVTZ and the optimized force field model fitted without the offset parameter δ in . (d), (e) and (f) are the optimized force field model fitted with the offset parameter δ in .

Illustration of the methanol cluster configurations used for the force field parameterization. Typical configurations of the (a) 9 molecules, (b) 11 molecules, and (c) 13 molecules of methanol are shown (the H atom is displayed in white, C atom in cyan and O atom in red). The interaction energy between the central molecule (circled by a dashed line) and the surrounding molecules is used in the optimization of the vdw parameters. (d) Distribution of interaction energies from MP2/6-31G(d,p) of 1,250 methanol clusters (999 clusters of 9 molecules, 157 clusters of 11 molecules, and 94 clusters of 13 molecules).