Thermal decomposition of a fullerene mix

A molecular dynamics study of impurity desorption from solid clusters of rigid C60 molecules

“…22 A shift of the transition temperature from face centered cubic to simple cubic structure of crystalline C 60 , 23 determined by the 'doping' of fullerite with He, N 2 , and O 2 , has been also reported. 19 Another interesting phenomenon, which has actually stimulated the present investigation, has been observed by several authors, [24][25][26][27][28] who have found that when C 60 crystals are heated at temperatures greater than 700°C and up to 900-1000°C, a considerable amount of amorphous carbon is produced, a circumstance which indicates that, under such conditions, C 60 molecules become unstable in the solid matrix. Since the isolated fullerene molecule is known to be highly stable, 29,30 the phenomenon does not have an immediate explanation.…”

“…34,[38][39][40][41] Since the calculated triple point temperature of this substance is ϳ1600 K, 34,38 an intrinsic instability of solid C 60 at much lower temperatures would in fact rule out any possibility to observe such a liquid phase by passing through the ''melting'' of fullerite. 27,28 The high temperature behavior of solidlike clusters of C 60 molecules and Kr atoms has been studied through MD simulation. Our study allows us to conclude that for ͗T͘ Ͻ1200 K, a fraction of the inert gas particles remains trapped inside the fullerite matrix, and that full desorption occurs only for ͗T͘Ӎ1500 K. The results of such an investigation can be considered extensible to other impurity species, with implications which have been discussed in connection with the observed amorphization of solid C 60 at high temperatures.…”

A Gibbs ensemble Monte Carlo study of phase coexistence in model C60

“…The possibility that residual impurities hosted in the solid matrix act to destabilize the C 60 molecule has been considered; 34 it has however been claimed that samples preliminary subjected to rather long purifying procedures at relatively high temperatures ͑500°C͒ exhibit nonetheless the same amorphization phenomenon. 34,36 Then, it has been conjectured that the high temperature instability is intrinsically correlated to the solid state assembling of the big-sized fullerene particles. 34 FIG.…”

Thermal behavior of a mixture of fullerenes and fullerites C60/70

“…In addition, it is much more difficult to isolate the diffraction lines of C 70 in the C 60/70 mix ture when the fraction of the X ray amorphous com ponent is high. Above 925°С the diffraction patterns contain only the X ray amorphous halo (at 2θ = 15°-24°), which was attributed [10,25] to fragments of decomposed fullerenes and graphite like planes.…”