Ab initio vibrational and thermal properties of carbon allotropes: Polycyclic and rectangular networks

Ab initio investigations of vibrational and thermal properties of carbon allotropes are performed using density functional theory calculations. Networks with different symmetries are investigated – polycyclic and rectangular structures. As infinite two dimensional sheets, the former class of systems present phononic gaps in the terahertz frequency domain, while one of the rectangular structures reveals a pseudogap in the same frequency range. Implications to the thermal transport are analyzed comparatively for nanoribbon systems, which indicate additional pseudogaps at lower frequencies. These are important for decreasing the thermal conductance, which is essential in the development of efficient thermoelectric devices.

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