Pressure-polymerization of C60 molecules in a carbon nanotube

The structural property of a C60-peapod sample under high pressure up to 25 GPa was investigated by in situ synchrotron X-ray diffraction measurements using a diamond anvil cell. It was observed that the C60-C60 distance in a carbon nanotube decreases with pressure from 0.956 nm at 0.1 MPa down to 0.845 nm at 25 GPa. It was also found that the distance value upon complete release of the pressure after compression remained at a value lower than its initial value. These experimental results indicate the polymerization of C60 molecules in a carbon nanotube.