STRUCTURAL PHASE TRANSITIONS IN (5, 5) CARBON NANOTUBE CONTROLLED BY ITS EXPANSION: CALCULATIONS BY THE MOLECULAR ORBITAL METHOD
The structure changes of metallic (5, 5) carbon nanotube at its expansion are calculated by the molecular orbital method. It is found that the ground state of the non-expanded nanotube is dielectric (phase A) as a result of Peierls distortions. The phase A has the Kekule structure with a triple translation period in comparison with the metallic phase (phase C). Two structural first order phase transitions are revealed. The transition between the phase A and intermediate phase B takes place at the elongation of 5 %. The transition between the phases B and C takes place at the elongation of 13 %. The metastable states are found for the phases A and B.