Graphical Gaussian Process Regression Model for Aqueous Solvation Free Energy Prediction of Organic Molecules in Redox Flow Battery

TL;DR

This paper introduces a Gaussian process regression model with a novel molecular graph kernel to accurately predict aqueous solvation free energy of organic molecules, aiding redox flow battery research.

Contribution

The work presents a new ML model with a molecular graph kernel and a dimension reduction algorithm to improve solvation energy prediction and address data scarcity issues.

Findings

Predicts solvation free energy with less than 1 kcal/mol MAE.

Effective in modeling electrostatic, nonpolar, and conformational effects.

Provides a method to select minimal training sets based on molecular graph diversity.

Abstract

The solvation free energy of organic molecules is a critical parameter in determining emergent properties such as solubility, liquid-phase equilibrium constants, and pKa and redox potentials in an organic redox flow battery. In this work, we present a machine learning (ML) model that can learn and predict the aqueous solvation free energy of an organic molecule using Gaussian process regression method based on a new molecular graph kernel. To investigate the performance of the ML model on electrostatic interaction, the nonpolar interaction contribution of solvent and the conformational entropy of solute in solvation free energy, three data sets with implicit or explicit water solvent models, and contribution of conformational entropy of solute are tested. We demonstrate that our ML model can predict the solvation free energy of molecules at chemical accuracy with a mean absolute error of less than 1 kcal/mol for subsets of the QM9 dataset and the Freesolv database. To solve the general data scarcity problem for a graph-based ML model, we propose a dimension reduction algorithm based on the distance between molecular graphs, which can be used to examine the diversity of the molecular data set. It provides a promising way to build a minimum training set to improve prediction for certain test sets where the space of molecular structures is predetermined.