New Insights on the Calculation of Contact Angles by Molecular Dynamics

Wettability, expressed through the contact angle (θ), is the key property governing solid-liquid interfacial phenomena. In this work, we employ the dimensionless parameter α, derived from the Steele 10-4-3 potential, as a predictive descriptor of wettability. Molecular Dynamics simulation results of a liquid on a model smooth surface show a consistent trend of α: increasing α monotonically decreases θ, irrespective of whether α is tuned via ε_w, σ_w, ρ_w, or Δ. This demonstrates that α provides a simple and transferable metric to anticipate wetting behavior and the onset of complete wetting. The reliability of this framework is further supported by comparisons with atomistically resolved surfaces and illustrated by the water-graphite experimental contact angle, which confirms that α captures the essential physics. Finally, an effective and practical methodology is introduced to describe smooth solid surfaces using implicit wall models and estimate the value of θ, enabling accurate wettability predictions for any pure liquid or liquid mixture over any smooth surface at significantly reduced computational cost.