The influence of nitrogen sorption on fullerite C₆₀ properties in a wide temperature range

The influence of nitrogen sorption on structural and thermodynamic properties of fullerite C₆₀ was studied using the powder x-ray diffraction methods under the gas pressure of 30 atm in the saturation temperature range 200-550 ^deg C. The kinetics of nitrogen sorption was studied at different temperatures by monitoring the time dependence of fullerite lattice parameter. It is found that the sorption mechanism is changed with increasing temperature. The diffusion mechanism of lattice void filling with nitrogen molecules at temperatures below 450 ^deg C goes way to a chemical interaction between nitrogen with fullerene molecules at higher temperatures, resulting in the formation of a new molecular material, namely, nitride fullerene C₆₀H_x. It is established that the transition from physical to chemical ab-sorption of nitrogen by fullerite (adsorption crossover) occurs in the temperature range 450 ^deg C > T > 400 ^deg C. It is shown that nitrogenation of C60 dramatically increases the volume of the C₆₀ cubic cell, decreases intensities of x-ray lines and increases their half-width. The maximum deformation levels of the fcc lattice, and the characteristic times of diffusion voids filling as well as the time of nitrogenation are determined. It is established that at nitrogenation decreases thermal expansion of solid C₆₀, suppresses both orientation phase transition and glass state formation