Process of intercalation of C60 with molecular hydrogen according to x-ray diffraction data

The process of normal hydrogen infusion into a C-60 powder at I bar and room temperature is monitored using x-ray diffraction. The effect of the intercalation on the lattice proves to be rather weak: the volume expansion upon complete saturation does not exceed 0.13%. The characteristic saturation time is found to be 320 h; the corresponding diffusion coefficient amounts to (2.8 +/- 0.8) X 10(-14) cm(2)/s. The integrated reflection intensity calculations for a completely saturated sample suggest that only octahedral voids are filled under the conditions of the experiment. Complete saturation has only a weak effect on the rotational subsystem of the C-60 fullerite: the orientational phase transition shifts by 6 to 7 K to lower temperatures; no substantial hysteresis is noticed. The dopant shows reluctance to leave the sample under a vacuum of 10(-3) Torr at room temperature. (C) 2009 American Institute of Physics. [DOI:10.1063/1.3081158]