(287b) ­Development of Accurate Potentials to Explore the Structure of Water on 2-D Materials

Water plays an important role in many biological and non-biological process. Structure of water at various interfaces and under confinement has always been the topic of immense interest. 2-D materials have shown great potential in surface coating applications and nanofluidic devices. However, the accurate atomic level understanding of the wettability of single layer of these 2-D materials is still lacking mainly due to lack of experimental techniques and computational methodologies including accurate force-field potentials and algorithms to calculate the contact angle of water. Here, we propose a new algorithm to calculate the accurate contact angle of liquid on a surface. By assuming the axisymmetric water droplet, all molecules were transformed from a 3-D space to a 2-D axisymmetric plane. Further, least-square fitting method was used to fit a circle through the 2-D axisymmetric plane. We employ this method of contact angle measurements to develop the accurate non-bonded potentials between water and graphene that reproduce the experimentally observed contact angle. Particle Swarm Optimization (PSO) algorithm has been employed to develop the non-bonded potentials between water and graphene. Different water models including SPC, SPC/E, SPC/Fw, and TIP3P were used to study the structure of water at the interface of graphene.