Dynamics of water in the hydration shells of C60:: Molecular dynamics simulation using a coarse-grained model

Dynamics of water in the solvation shells of a fullerene molecule as obtained from a coarse-grained (CG) model for the C-60-water interaction has been presented and compared with the same obtained from the atomistic model. While in the CG model the interaction between a fullerene and a water has been represented by a simple two-body central potential as obtained from a coarse-graining of the interactions of a C-60 molecule with water, in the atomistic description all the interactions between the atoms of a C-60 and a water molecule have been explicitly taken into account. Extensive molecular dynamics simulations of a C-60 molecule in water have been performed in isothermal-isobaric ensembles. Translational and reorientational mobilities as well as residence time of water in the solvation shells of a fullerene molecule have been obtained by calculating the corresponding time correlation functions from simulation trajectories. Comparison of the dynamical behaviors obtained from the CG and the atomistic models shows overall good agreement. The nature of the relaxation and the trend that the dynamics becomes slower with the decreasing solute-water distance as obtained from the atomistic model have, in general, been reproduced by the CG model.