Dynamics of H$_{2}$O Molecules Confined in Fullerenes

Structural and dynamical properties of confined water in nanostructures are expected to be remarkably different than those of bulk water. Water confined in nanotubes and graphene sheets has been extensively investigated theoretically, yet very few computational efforts have been made to study confined water in fullerenes though, experimentally, water molecules have been successfully encapsulated inside fullerenes as small as C$_{60}$. In this work, we carry out classical molecular dynamics simulations to investigate density and H-bond distributions inside fullerenes ranging from C$_{60}$ to C$_{540}$. Our results show that as the size of the fullerene increases, concentric shells of water molecules are formed, and the water density is higher than that of bulk water while the average H-bond per molecule is slightly lower than the bulk value. We also find that these shells of H$_{2}$O are solid-like at room temperature, but they should eventually become liquid-like at high temperatures.