# Nuclear quantum effects in molecular liquids across chemical space

## TL;DR

This study explores how nuclear quantum effects influence the properties of 92 organic liquids using simulations and identifies key factors that predict these effects.

## Contribution

The study systematically quantifies nuclear quantum effects in a broad range of organic liquids and identifies predictive features for these effects.

## Key findings

- NQEs significantly impact thermal expansivity, compressibility, and molar volume of organic liquids.
- Molar mass, hydrogen density, and thermal expansivity are key predictors of NQEs in organic liquids.
- Deuteration leads to less pronounced isotope effects compared to full quantum effects.

## Abstract

Nuclear quantum effects (NQEs) influence many physical and chemical phenomena, particularly those involving light atoms or occurring at low temperatures. However, their impact has been carefully quantified in few systems-like water-and is rarely considered more broadly. Here we use path-integral molecular dynamics to systematically investigate NQEs on thermophysical properties of 92 organic liquids at ambient conditions. Depending on chemical constitution, we find substantial impact across thermal expansivity, compressibility, dielectric constant, enthalpy of vaporization, and notably molar volume, which shows consistent, positive quantum-classical differences up to 5%; similar, less pronounced trends manifest as isotope effects from deuteration. Using data-driven analysis, we identify three features-molar mass, classical hydrogen density, and classical thermal expansivity-that accurately predict NQEs and facilitate understanding of how characteristics like branching and heteroatom content influence behavior. This work highlights the broad relevance of NQEs in molecular liquids, while also providing a conceptual and practical framework to anticipate their impact.

Nuclear quantum effects affect chemical processes and material properties. Here the authors use path-integral molecular dynamics simulation to analyze their effects on themophysical properties of 92 organic liquids across the chemical space.