Theoretical study of a body-centered-tetragonal phase of carbon nitride

We present the results of a theoretical study of a body-centered-tetragonal (BCT) phase of carbon nitride (CN) with 1:1 stoichiometry using a self-consistent-charge density-functional tight-binding method. This CN phase is highly stable and has a small $c/a$ ratio of 0.34 with complicated N and C dimerization along the c axis. The N atoms form a quasi-one-dimensional polymeric chain structure. Bond lengths as short as $1.16\hspace{0.5em}\AA$ between C atoms and $1.11\hspace{0.5em}\AA$ between N atoms are obtained along the c axis. However, the bond lengths in the $a-b$ plane are considerably longer, yielding only a modest bulk modulus of 243 GPa. We examine the structural and electronic properties to characterize and understand this CN phase.