(594e) Understanding Water Slip on Defective Boron Nitride Surfaces: Combined Quantum and Classical Modeling of Solid–Liquid Friction

Defects such as atomic vacancies are commonly encountered in real two-dimensional (2D) materials, yet their effect on interfacial phenomena is seldom considered. In this work, we realistically model the frictional properties of hexagonal boron nitride (hBN), an up-and-coming 2D material, by considering five different types of vacancy defects present in it. In recent years, hBN has been employed in various applications, such as membrane separations and energy harvesting, where hBN–water interfaces are ubiquitous. Thus, understanding solid–liquid friction on realistic hBN surfaces is important to design and develop such applications. Here, we present a combined quantum-classical approach to achieve this objective. To this end, we use quantum-mechanical density functional theory (DFT) to obtain point charges to accurately represent the unique electric field produced by each of the five defects considered. Subsequently, using classical molecular dynamics (MD) simulations, we study the role of the vacancy size and composition in modulating the hBN–water friction coefficient, and the resultant slip length for water flow on hBN. We also quantify the effect of vacancy concentration on the hBN–water friction coefficient. Our work provides realistic limits for the friction coefficient of hBN, by considering the effect of the most-probable defects in that material.