LAUSR

Abstract In this work, we have introduced defects like bond rotation and the sifting of atoms along the non-bonding direction in graphene to come up with a new dynamically stable crystal with a 5-4-4-5 ring geometry. However, on thermal excitation, the system transforms into a thermodynamically more stable phase with a 5-6-5 ring (PHP) structure belonging to Pmmm space group. This unprecedented PHP carbon system with 12 atomic sites in the unit cell resembles the extended s-indacene skeleton. Furthermore, we have explored that the pristine system is metallic with both electron and hole pockets in the Brillouin zone (BZ). However, its stable isostructural carbon nitrides exhibit various electronic properties like metallic, semimetallic and semiconducting. The emergence of Dirac fermions, in particular, carbon nitride, has judicially been explained by introducing an elegant analytical approach in terms of the real space renormalization group (RSRG) scheme in the tight-binding (TB) framework. Moreover, some carbon nitrides induce tunable bandgap in the system depending on the doping sites. Besides, the optical absorption spectra depict the strong response in the visible to ultraviolet range. Finally, the proposed system offers various preferable sites for Li adsorption and serves as an anchoring material for Li-ion battery applications.