A molecular dynamics study of impurity desorption from solid clusters of rigid C-60 molecules

We investigate through molecular dynamics (MD) simulation the desorption at high temperature of Kr atoms from solidlike clusters of rigid C-60 molecules. The inert gas particles are initially allocated in the interstices of a solid C-60 matrix, placed at the center of the simulation box with empty space around; desorption is then monitored as a function of the average temperature achieved at the end of different MD run. The assumed sphericalized two-body potential practically excludes endohedral absorption of Kr inside the fullerene cage and is potentially suitable to model impurity species other than the one here considered. The obtained results indicate that in the range of temperatures 1200 less than or equal to T less than or equal to 1500 K the solid matrix of C-60 articles is stable, and that only a part of the 'doping' Kr atoms is able to escape from the C-60 'environment', the rest remaining trapped inside the fullerene cluster in a configuration in which the rare gas atoms occupy on the average the octahedral sites of the host matrix. The implications of such results as far as the role of impurity species in determining the experimentally observed high temperature instability of fullerites accompanied by carbon amorphization, are discussed. (C) 1997 American Institute of Physics.