Theoretical Study Of Ordered Water And Self-diffusion Behavior Of Surrounding Water Molecules

Ordered water structures confined to two dimensions have been found and extensively studied by experimental or theoretical methods.It has been realized that this ordered water not only exhibits novel behavior but also affects various surface properties,such as the surface electrochemical property,surface wetting behavior and surface friction,etc.In our research work,these two surfaces are both planar hexagonal structures,but the bond lengths between carbon atoms are different.We find that the water molecules diffuse faster on top of the ordered water molecules near the surface,which is due to the reduction of hydrogen bonds between the water molecules in the ordered water layer and the water molecules above this layer.These water molecules with the ordered water structures also characterize much slower relaxation time of water dipole and longer lifetime of hydrogen bonds in the first layer.In this work,we have studied the diffusion behavior,dynamics of hydrogen bonds and the structure of water molecules on different types of surfaces via molecular dynamic simulations.Generally,the diffusion of water molecules we have studied is partly determined by interfacial interaction,which is usually a source of surface hydrophilicity or hydrophobicity,so in general we think that the diffusion on the hydrophobic surface is faster than that on the hydrophilic surface.Our work is in contrast to the conventional view of slower self-diffusion near the hydrophilic solid surface and provides a new way to enhance the water self-diffusion near the hydrophilic surfaces.Considering that the room temperature ordered water has been found extensively existing on a variety of materials surfaces,our work will have an important impact on nanomaterials and other fields.