Compressibility of CO intercalated C-60 crystals

We report the pressure dependence of the cubic lattice parameter of (CO)(x) C-60 at different temperatures, as determined by X-ray powder diffraction. In the measured range of pressures from 0.2 to 2 GPa, the volume is found t o depend linearly on the pressure. The extrapolated volume bulk modulus of the ordered phase at room temperature is found to be K-0 = - V dP/dV = 31.5 (5) Cpa. The bulk modulus at T = 150 K is found as K-0 = 26.9(5) GPa. The g reater stiffness at higher temperature is explained by the entropic contrib ution of the CO molecules to the bulk modulus. (C) 2000 Elsevier Science B. V. All rights reserved.