Automated Topology Builder Version 3.0: Prediction of Solvation Free Enthalpies in Water and Hexane.

The ability of atomic interaction parameters generated using the Automated Topology Builder and Repository version 3.0 (ATB3.0) to predict experimental hydration free enthalpies (Δ Gwater) and solvation free enthalpies in the apolar solvent hexane (Δ Ghexane) is presented. For a validation set of 685 molecules the average unsigned error (AUE) between Δ Gwater values calculated using the ATB3.0 and experiment is 3.8 kJ·mol-1. The slope of the line of best fit is 1.00, the intercept -1.0 kJ·mol-1, and the R2 0.90. For the more restricted set of 239 molecules used to validate OPLS3 ( J. Chem. Theory Comput. 2016 , 12 , 281 - 296 , DOI: 10.1021/acs.jctc.5b00864 ) the AUE using the ATB3.0 is just 2.7 kJ·mol-1 and the R2 0.93. A roadmap for further improvement of the ATB parameters is presented together with a discussion of the challenges of validating force fields against the available experimental data.