Elastic and dissipative properties of solid C60

Elastic and dissipative properties of solid C60 in the face centered cubic (fcc) and high pressure induced phases were measured on the same specimens. The high pressure phase was synthesized in our experiments by the thermobaric treatment of specimens at temperature of 350 C and under pressure of 2 GPa. The structure investigations revealed the origination of the chemical bonding between C60 molecules in that phase. The measurements of attenuation and velocities of longitudinal and transverse sound waves were carried out in the temperature range from 4.2 to 300 K at the frequencies of 5 and 10 MHz by echo pulse and high frequency resonance methods. It was found that the values of elastic moduli of the new phase, measured at room temperature, appeared two times higher and their temperature dependences two times weaker than corresponding ones of the pristine C60. The internal friction spectrum of fcc phase differs significantly from that of hpp phase. The phenomena observed are discussed in terms of model taking into account the formation of polymer chains in the structure of the new pressure-induced phase of solid C60. (orig.)