Molecular dynamics simulations of noble gases encapsulated in C60 Fullerene

Molecular dynamics simulations of Helium (He), Neon (Ne), Argon (Ar), Krpton (Kr) and Xenon (Xe) encapsulated in C-60 are discussed, as well simulations of Fullerenes containing anywhere from two to four He atoms. Even for single atom encapsulates, no species resides at the geometric center of the Fullerene cage. Smaller atoms sit more off-center than larger ones, and He appears to be a special case in both centering and dynamics. Some encapsulated species stabilize the cage by stifling radial fluctuations and others disrupt it; adding Ne seems to have the most stabilizing effect, while Kr and Xe cause the largest radial atomic excursions. Multiple He encapsulates tend to stabilize the cage; such systems are very stressed and show structure over a wide temperature range. Based on dynamical information quadruple He seems to be close to the packing limit for C-60.