NMR Chemical Shifts in Hard Carbon Nitride Compounds

We show that NMR chemical shift spectroscopy could help to identify the crystalline phases of hard carbon nitride compounds. To this purpose we compute the NMR chemical shifts of defect zinc-blende, cubic, $\alpha -$, $\beta -$, and graphitic ${\mathrm{C}}_3{\mathrm{N}}_4$ with a newly developed ab initio method. The C shifts can be used to identify the CN bonds and to characterize C hybridization. The N shifts distinguish the $\alpha -{\mathrm{C}}_3{\mathrm{N}}_4$ from the $\beta -{\mathrm{C}}_3{\mathrm{N}}_4$ phases, and indicate the presence of the graphitic phase.