High-dimensional neural network potentials for solvation: The case of protonated water clusters in helium

TL;DR

This paper introduces a neural network potential combined with pairwise additive models to accurately simulate helium-solute interactions in superfluid helium, enabling efficient and precise studies of solvation effects on complex molecules.

Contribution

The authors develop a high-dimensional neural network potential for helium-solute interactions that is highly accurate and automatable, improving upon previous methods for simulating solvation in superfluid helium.

Findings

Achieves mean absolute deviation of 0.04 kJ/mol compared to CCSD(T) calculations.

Accurately reproduces many-body distribution functions for microsolvation.

Effective for modeling solvation of protonated water clusters in helium.

Abstract

The design of accurate helium-solute interaction potentials for the simulation of chemically complex molecules solvated in superfluid helium has long been a cumbersome task due to the rather weak but strongly anisotropic nature of the interactions. We show that this challenge can be met by using a combination of an effective pair potential for the He-He interactions and a flexible high-dimensional neural network potential (NNP) for describing the complex interaction between helium and the solute in a pairwise additive manner. This approach yields an excellent agreement with a mean absolute deviation as small as 0.04 kJ/mol for the interaction energy between helium and both, hydronium and Zundel cations compared to CCSD(T) reference calculations with an energetically converged basis set. The construction and improvement of the potential can be performed in a highly automated way, which opens the door for applications to a variety of reactive molecules to study the effect of solvation on the solute as well as the solute-induced structuring of the solvent. Furthermore, we show that this NNP approach yields very convincing agreement with the CCSD(T) reference for properties like many-body spatial and radial distribution functions. This holds for the microsolvation of the protonated water monomer and dimer by a few helium atoms up to their solvation in bulk helium as obtained from path integral simulations at about 1 K.