Modeling Nuclear Quantum Effects on Long Range Electrostatics in Nonuniform Fluids

TL;DR

This paper investigates how nuclear quantum effects influence long-range electrostatics in nonuniform water systems, revealing that quantum water exhibits stronger electrostatic forces for similar interfacial screening, using combined path integral and local molecular field theories.

Contribution

It introduces an efficient approach combining path integral simulations with local molecular field theory to model nuclear quantum effects on electrostatics in nonuniform systems.

Findings

Quantum water requires larger electrostatic forces for equivalent interfacial screening.

The developed methods efficiently describe long-range electrostatics in quantum systems.

Nuclear quantum effects significantly alter electrostatic interactions at interfaces.

Abstract

Nuclear quantum effects play critical roles in a variety of molecular processes, especially in systems that contain hydrogen and other light nuclei, such as water. For water at ambient conditions, nuclear quantum effects are often interpreted as local effects resulting from a smearing of the hydrogen atom distribution. However, the orientational structure of water at interfaces determines long range effects like electrostatics through the O-H bond ordering that is impacted by nuclear quantum effects. In this work, I examine nuclear quantum effects on long range electrostatics of water confined between hydrophobic walls using path integral simulations. To do so, I combine concepts from local molecular field (LMF) theory with path integral methods at varying levels of approximation to develop an efficient and physically intuitive approaches for describing long range electrostatics in nonuniform quantum systems. Using these approaches, I show that quantum water requires larger electrostatic forces to achieve the same level of interfacial screening as the corresponding classical system. This work highlights subtleties of electrostatics in nonuniform classical and quantum molecular systems, and the methods presented here are expected to be of use to efficiently model nuclear quantum effects in large systems.