Assessing van der Waals Corrections in the Description of Water Adsorption and Diffusion on Graphene and Hexagonal...

A comprehensive first-principles investigation was conducted to assess the performance of distinct van der Waals (vdW) correction schemes in describing the structural, energetic, and dynamical properties of water adsorption on graphene and hexagonal boron nitride monolayers. The PBE functional was complemented by both empirical (D2, D3, D3BJ) and nonlocal (DF1, DF1C09, DF2, DF2C09) functionals to assess how dispersion affects adsorption and diffusive behavior at solid-liquid interfaces. The combination of static structural optimizations, ab initio molecular dynamics, and climbing-image nudged elastic band calculations provides a comprehensive picture of the weak physisorption profile. The analysis reveals that even though empirical schemes enhance binding relative to bare PBE and generally reproduce the correct energetic scale, their accuracy varies depending on the substrate, whereas selected nonlocal vdW-DF approaches reproduce equilibrium geometries and diffusion trends reasonably well, albeit with larger deviations in adsorption energetics relative to high-level many-body benchmarks. Among the tested schemes, D3 and D3BJ provide the closest agreement with benchmark adsorption energies derived from diffusion Monte Carlo and random-phase approximation calculations. DF2 reproduces the weak physisorption regime and equilibrium adsorption geometries with reasonable accuracy; however, it systematically predicts stronger interaction energies than the many-body reference methods and slightly amplifies the energetic distinction between graphene and hBN. Ab initio molecular dynamics simulations confirm the thermal stability and high lateral mobility of water on both surfaces, which are associated with shallow diffusion barriers below 20 meV. These findings highlight the critical role of long-range correlation in modeling polar molecules on 2D materials and establish a quantitative framework for selecting vdW corrections in density functional theory studies of solid-liquid interfaces.