The geometric and electronic transitions in body-centered-tetragonal C8: A first principle study
Hui-Juan Cui ^{a, b}, Qing-Bo Yan ^{a, c}, Xian-Lei Sheng ^d, Dong-Lin Wang ^a, Qing-Rong Zheng ^a, *, Gang Su ^{a, e,} **
^a Theoretical Condensed Matter Physics and Computational Materials Physics Laboratory, School of Physics, University of Chinese Academy of Sciences,
Beijing, 100049, China
^b Institute of Applied Physics and Computational Mathematics, Beijing, 100088, China
^c College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
^d Department of Physics, Key Laboratory of Micro-Nano Measurement-Manipulation and Physics, Beihang University, Beijing, 100191, China
^e Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences, Beijing, 100190, China

The stability, geometric structure and electronic properties of a novel body-centered tetragonal carbon allotrope Bct C8 are systematically investigated. Bct C8 are formed by sp3-bonded carbon atoms and can be regarded as a compressed bundle of carbon nanotubes (CNT). The transition path from CNT to Bct C8 has been simulated, indicating a possible approach to synthesize Bct C8. The X-Ray diffraction, phonon and Raman spectroscopies are presented as reference for experimental studies. Besides, Bct C8 is a semiconductor with an indirect gap of 1.66 eV and will transform to semimetal when doping with boron and nitride atoms. Furthermore, considering its porous structural character, the lithium storage capability of Bct C8 are also discussed, a directional fast lithium-ion mobility with a rather low 0.04 eV barrier is revealed. Therefore, the Bct C8, once synthesized experimentally, would have fruitful applications in carbon-based electronics and energy storage.