Accessing the Accuracy of Density Functional Theory through Structure and Dynamics of the Water–Air Interface

TLDR

Density‑functional‑theory molecular dynamics are widely used to simulate aqueous interfaces, yet the choice of functional—critical to results—remains arbitrary, and the heterogeneous interactions governing water–air interfacial structure and dynamics provide a key benchmark. The study evaluates the performance of different exchange–correlation functionals using sum‑frequency generation spectroscopy metrics. The authors benchmark XC functionals by comparing their predictions to sum‑frequency generation spectroscopy metrics. The study shows that revPBE and revPBE0 functionals with dispersion corrections excel, while the empirically optimized M06‑L performs poorly, underscoring the importance of exact functional conditions and aiding resolution of interfacial water structure controversies and future functional design.

Abstract

Density functional theory-based molecular dynamics simulations are increasingly being used for simulating aqueous interfaces. Nonetheless, the choice of the appropriate density functional, critically affecting the outcome of the simulation, has remained arbitrary. Here, we assess the performance of various exchange–correlation (XC) functionals, based on the metrics relevant to sum-frequency generation spectroscopy. The structure and dynamics of water at the water–air interface are governed by heterogeneous intermolecular interactions, thereby providing a critical benchmark for XC functionals. We find that the XC functionals constrained by exact functional conditions (revPBE and revPBE0) with the dispersion correction show excellent performance. The poor performance of the empirically optimized density functional (M06-L) indicates the importance of satisfying the exact functional condition. Understanding the performance of different XC functionals can aid in resolving the controversial interpretation of the interfacial water structure and direct the design of novel, improved XC functionals better suited to describing the heterogeneous interactions in condensed phases.