Quantum Chemistry Study On The Effect Of Medium Silica On The Stability Of Hydrate Cage On Its Surface

This study is about the influence of hydrate rings?four-membered ring,five-membered ring and six-membered ring?of different hydrated cage structures(CH₄@4³5⁶6³ and CH₄@5¹²6²)interacting with different surfaces?100 surface,111 surface?of medium silica with two kinds of ways?single ring parallel way and double rings inserted way?on the stability of the hydrate cages,investigated by density functional theory in quantum chemistry.Various energies were calculated,such as the interaction energy between the silica surface and cage,the deformation energy of the hydrate cage,the interaction energy between the methane molecule and the cage and the interaction energy between the water molecules within the cages.The results indicate that there are strong inter-molecular interaction forces between the hydrated cages and surfaces of silica both in single ring parallel way and in double ring inserted way,and the interactions are mainly manifested as hydrogen bond form through the way of structural matching between the Si-OH and Si-H on the silica surface and the water molecules in the hydrated cage.These interactions are affected by the contact ways between the hydrated cage and the surface of the silica,the oxygen atom density on the silica surface,the extent of structure match between contacted area,and the ring's size and its stability et al.On the one hand,the interactions would result in the cage deformation and weakening the binding force within the cage.On the other hand,the interactions could lessen the attraction between the inner methane molecule and the cage.Both of these effects will cause the methane molecules overflow from the cage easily.