Toward Chemical Accuracy in the Description of Ion–Water Interactions through Many-Body Representations. I. Halide–Water Dimer Potential Energy Surfaces

• Published in: Journal of chemical theory and computation Vol. 12; no. 6; pp. 2698 - 2705
• Main Authors: Bajaj, Pushp, Götz, Andreas W, Paesani, Francesco
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.06.2016
• Subjects: Accuracy; Dimers; Dynamical systems; Dynamics; Mathematical models; Molecular structure; Phases; Potential energy
• ISSN: 1549-9618; 1549-9626
• DOI: 10.1021/acs.jctc.6b00302

Despite recent progress, a unified understanding of how ions affect the structure and dynamics of water across different phases remains elusive. Here, we report the development of full-dimensional many-body potential energy functions, called MB-nrg (Many-Body-energy), for molecular simulations of halide ion–water systems from the gas phase to the condensed phase. The MB-nrg potentials are derived entirely from “first-principles” calculations carried out at the F12 explicitly correlated coupled-cluster level including single, double, and perturbative triple excitations, CCSD­(T)-F12, in the complete basis set limit. Building upon the functional form of the MB-pol water potential, the MB-nrg potentials are expressed through the many-body expansion of the total energy in terms of explicit contributions representing one-body, two-body, and three-body interactions, with all higher-order contributions being described by classical induction. The specific focus of this study is on the MB-nrg two-body terms representing the full-dimensional potential energy surfaces (PESs) of the corresponding H2O–X– dimers, with X–= F–, Cl–, Br–, and I–. The accuracy of the MB-nrg PESs is systematically assessed through extensive comparisons with results obtained using both ab initio models and polarizable force fields for energies, structures, and harmonic frequencies of the H2O–X– dimers.