Theoretical prediction of maximum capacity of C80 and Si80 fullerenes for noble gas storage

In this paper, we try to demonstrate that how many helium, neon and argon atoms can be trapped into fullerene cages until the pressure becomes large enough to break the C-80 and Si-80 frameworks. The maximum number of helium, neon and argon atoms which can be encapsulated into C-80 fullerene, is found with 46, 24 and 10 atoms respectively. Having investigated the mechanism of C-80 opening, we found that if the number of helium and argon atoms reaches to 50 and 12 respectively, the C-C bonds of C-80 are broken and the gas molecules escaped from the fullerene cage. The final optimization geometries of latter complexes are similar to the shopping cart. Therefore, this appearance is named as molecular cart. Moreover, the maximum capacity of Si-80 fullerene for encapsulated noble gas atoms is found 95, 56 and 22 for helium, neon and argon atoms correspondingly. It is worth highlighting that the new phenomenon of trapping argon atoms into Si-80 cage is observed, when a Si atom randomly added to the center of Ar-19@Si-80 structures. In this case, the Si Si bonds of Si-80 are broken and two argon atoms will escape from the cage. After that, the framework rebuilds its structure like the initial one. This phenomenon is introduced as molecular cesarean section. The estimated internal pressure of Ng atoms trapped into the fullerene cages is also investigated. Results show that the maximum calculated internal pressure is related to He-46@C-80 and He-95@Si-80 structures with 212.3 and 144.1 GPa respectively. (C) 2014 Elsevier Inc. All rights reserved.