Model for compression of fullerenes and carbon nanotubes

The new materials of carbon, solid C-60 and carbon nanotubes (CNT) [1,4] are important for various technological applications. One of the reasons for their technological applications could be based upon the fact that they have a lot of empty space in their molecules as well as in their unit cells when bulk quantities of these are taken in the form of either C-60 solid or nanoropes. Their compressibility studies have revealed extremely interesting results showing tremendous reversible compression which has aroused curiosity and interest. CNT have been found to be compressible reversibly up to about 65% of their original volume when subjected to pressures of about 20 kbar. This enormous volume compression in such materials under moderate pressures is conceived to be of great significance for understanding and interpreting the mechanism based on molecular level understanding related to shock compression in these materials. We undertake a model study accounting for unit cell deformations by applying pressures up to 3 Gpa and develop a pressure compression relation. We use the anharmonicity of the intermolecular potential energy to calculate Gruneisen parameters and the temperature increase due to an adiabatic pressure application. This work uses some components calculated from a rigid molecule model, whereas others are taken from experimental pressure compression data.