Temperature dependence of elastic moduli for solid C-60

The attenuation and velocity of ultrasonic waves (at a frequency of similar to4 MHz) along the < 111 > and < 100 > directions in solid C-60 single-cry stal samples are measured in the temperature range 100-300 K. The temperatu re dependences of the complete set of elastic constants for C-60 fullerite are determined from the experimental data. It is shown that the specific fe atures in the behavior of the elastic moduli near the orientational phase t ransition temperature are associated with different contributions of the re laxation processes to the effective elastic moduli. The activation volume a nd deformation potentials for the ground and excited states of the C-60 low -temperature phase are evaluated from the results obtained in this work and the data available in the literature. (C) 2001 MAIK "Nauka/Interperiodica" .