Encapsulation of Methane Molecules into C60 Fullerene Nanocage: DFT and DTFB-MD Simulations

Extensive urbanization has greatly raised the demand for cleaner coal- and petroleum-derived fuels. Mainly composed of methane, natural gas represents a promising alternative for this purpose, making its storage a significant topic. In the present research, deposition of methane molecules in C60 fullerene was investigated through a combined approach wherein density functional based tight binding (DFTB) method was used to optimize the geometry while ab initio density functional theory (DFT) served as a tool for energy calculation. Doping endohedral methane molecules onto fullerene nanocage, it was witnessed that, the only stable complex might be formed by a single methane molecule entrapped inside the C60 cage. It was further indicated that, when a large number of encapsulated CH4 molecules are concerned, occasional chemisorption of the molecules on the inner surface of the cage would occur, ending up breaking the capsule side wall at NCH4=7. Further studied by density-functional tight-binding molecular dynamics (DFTB-MD) simulation, mechanism of the breakage indicated this complex as being highly unlikely to be stable.