Low Temperature Features of Sound Velocity in Fullerite C60 Orientational Glasses

The nature of the linear term in the heat capacity in fullerite C-60 was studied. The low-temperature dependence of the sound velocity was determined from the data of the heat capacity at temperatures below 10 K. A model of the dynamic configuration excitations (DCE) was proposed to describe the contribution to the heat capacity of the linear term in heat capacity and calculation of the dependence of sound velocity. It was shown that the model adequately described the dynamics of the cluster formations of the short-range order in fullerite C-60 because it took into account the excitations of both the atomic and electronic subsystems. In the framework of this model, it was shown that the low-energy tunnel states that were located at the boundaries of C-60 domains made a dominant contribution to low-temperature effects in the heat capacity and sound velocity of C-60.