Ultrasonic study of monomeric fullerite C60 under pressure

Abstract

The ultrasonic study of the elastic moduli of polycrystalline fullerite C60 was carried out in the temperature range from liquid nitrogen to room temperature at pressures up to 1.4 GPa, including the regions of the orientational fcc-to-sc and glass transitions. The temperature dependencies of the elastic moduli at ambient pressure are in good agreement with previous studies. For the first time the pressure dependencies of the shear modulus and Poisson's ratio were determined. Particularly, the Poisson's ratio was found to increase from ≈0.3 at ambient pressures to ≈0.38 at p = 1 GPa. The observed high values of the Poisson's ratio, as well as the high values of pressure derivatives of the bulk modulus ≈23-25 are discussed in terms of the central m-n power potential and contribution of the non-central intermolecular forces due to intramolecular deformations. © 2008 IOP Publishing Ltd.