The influence of hydrogen sorption in fullerite C60 at pressure of 30atm and saturation temperature of 150-380C on its structural and thermodynamic properties was studied using X-ray powder diffraction and photoluminescence methods. The kinetics of hydrogen sorption at different temperatures was studied by monitoring the time dependence of the fullerite lattice parameter. It was found that the sorption mechanism undergoes change upon the temperature increase. Diffusion-controlled filling of the cavities in fullerite lattice with hydrogen molecules at temperatures T ≤ 250C was replaced by chemical interaction between hydrogen and fullerene molecules at higher temperatures, resulting in the formation of a new molecular material: hydrofullerite C60Hx. It was established that the transition from physisorption to chemisorption of hydrogen by fullerite (adsorption crossover) occurred in the temperature range 300C > T > 250C. The hydrogenation of C60 was shown to dramatically increase the volume of the C60 cubic cell, decrease the thermal expansion of the crystals, and suppress the orientational transition and formation of a glass state. The maximum deformation levels of the face-centered cubic lattice as well as the characteristic times of voids filling and hydrogenation were determined for the cases of diffusion-controlled void filling and chemisorption, respectively.

Saturation of Fullerite C60 with Hydrogen: Adsorption Crossover Studies. Yagotintsev, K.A., Legchenkova, I.V., Stetsenko, Y.E., Zinoviev, P.V., Zoryansky, V.N., Prokhvatilov, A.I., Strzhemechny, M.A.: Low Temperature Physics, 2012, 38[10], 952-6