Phase Transitions and the Structure of the C_(60) Crystal Doped with Lithium by Electrodiffusion

摘要

The structure and phase transitions of C_(60) crystals doped with lithium by injecting metal ions from the superionic crystal-C_(60) single crystal heterojunction under electrodiffusion conditions are reported. The sample experienced irreversible transitions resulting in the virtually complete disappearance of EPR signals and MW conduction in the temperature range 320-370 K. In this temperature interval, a new C_(60) phase was formed; the phase contained polymeric chains of C_(60) molecules along the crystallographic c axis and lithium clusters. The structure of this phase was determined. Annealing at 620 K restored the EPR signal and, according to the X-ray data, the initial cubic structure of pure C_(60). The X-ray pattern, however, contained additional diffraction peaks, which was evidence of the presence of one more phase with a structure yet unknown.