Abstract
The structure and dynamic properties of interfacial water at the graphite and silica solid surfaces were
investigated using molecular dynamics simulations. The effect of surface properties on the characteristics of
interfacial water was quantified by computing density profiles, radial distribution functions, surface density
distributions, orientation order parameters, and residence and reorientation correlation functions. In brief, our
results show that the surface roughness, chemical heterogeneity, and surface heterogeneous charge distribution
affect the structural and dynamic properties of the interfacial water molecules, as well as their rate of exchange
with bulk water. Most importantly, our results indicate the formation of two distinct water layers at the SiO2
surface covered by a large density of hydroxyl groups. Further analysis of the data suggests a highly confined
first layer where the water molecules assume preferential hydrogen-down orientation and a second layer whose
behavior and characteristics are highly dependent on those of the first layer through a well-organized hydrogen
bond network. The results suggest that water-water interactions, in particular hydrogen bonds, may be largely
responsible for macroscopic interfacial properties such as adsorption and contact angle.