(515j) Using Polarizable Force Field-Based Molecular Dynamics Simulations to Model the Wetting of Hexagonal Boron Nitride Surfaces By Water

Hexagonal boron nitride (hBN) possesses outstanding attributes, including high thermal conductivity, wide band gap, and thermal stability, which have sparked significant scientific interest in this material. Many practical applications involving hBN, including seawater desalination, nanofluidic energy generation, biological sensing, and chemical separations, require that the hBN surface interacts with various liquids, with water being the most prevalent. Although polar water is expected to generate a finite electric field at an hBN/water interface, leading to the polarization of the charge distribution of the hBN surface, there remains a significant gap in understanding how this polarization controls the wetting ability of water on hBN surfaces.

With the above in mind, we developed a theoretical framework ^[1,2] that incorporates an all-atom polarizable force field to precisely capture the anisotropic polarizability tensor of hBN along with its interactions with water. This force field can self-consistently model the polarization of hBN induced by the electric field exerted by the water molecules using the classical Drude oscillator model. By carrying out Molecular Dynamics (MD) simulations, we investigated how the many-body polarization interactions influence the wetting properties of hBN surfaces by water. Our results show that this new force field predicts a water contact angle of 83.1^â—¦ on hBN surfaces which is consistent with the recently reported experimental contact angle of 79.0^{â—¦ [3]}. In contrast, using a Lennard-Jones (LJ) potential to model the water-hBN interactions, a commonly used approximation, predicted a significantly lower water contact angle of 67.8^â—¦[2]. We also found that incorporating the polarization response of hBN increases the number of water molecules adopting a 1 Leg orientation (with one of the hydrogen atoms pointing towards hBN) at the hBN surface, thereby increasing the interfacial entropy of water, an effect which is not observed when the polarization energy is modeled implicitly using the LJ potential.

References

1. Misra, R. P.; Blankschtein, D. Insights on the Role of Many-Body Polarization Effects in the Wetting of Graphitic Surfaces by Water. J. Phys. Chem. C 2017, 121(50), 28166−28179.
2. Luo, S.; Misra R. P.; Blankschtein D. Water Electric Field Induced Modulation of the Wetting of Hexagonal Boron Nitride: Insights from Multiscale Modeling of Many-Body Polarization. ACS Nano 2024, 18, 1629−1646.
3. Yang, F.; McQuain, A. D.; Kumari, A.; Gundurao, D.; Liu, H., Li, L. Understanding the Intrinsic Water Wettability of Hexagonal Boron Nitride. Langmuir 2024, 40(12), 6445−6452.