Elastic and other associated properties ofC60

Considering that Coulomb interactions contribute a negligible amount to the cohesive energy in ${\mathrm{C}}_{60}$, which has an fcc structure at room temperature, we used Girifalco potential function in our calculations; ${\mathrm{C}}_{60}$ is spherical in nature and rotates rather freely at room temperature. From this potential we evaluated the second-order elastic constants (SOEC's), their pressure derivatives, and the third-order elastic constants (TOEC's). The SOEC's are found to be in good agreement with other literature values reported so far. The pressure derivative of bulk modulus is found to be 3.8 which compares favorably with Duclos values while the theoretical literature value is reported to be high. The pressure derivatives of the SOEC's are found to be high compared with those of glassy, amorphous materials, alloys, and metals. Furthermore, the derivatives are all found to be positive. The TOEC's are all found to be negative resembling those of polymers like polystyrene. We evaluated the thermal Gruneisen's constant from the potential function and the value obtained is in excellent agreement with experiment.