First-principles investigation of graphitic carbon nitride monolayer with embedded Fe atom

Density functional theory calculations with spin-polarized generalized gradient approximation and Hubbard U correction is carried out to investigate the mechanical, structural, electronic and magnetic properties of graphitic heptazine with embedded Fe atom under bi-axial tensile strain and applied perpendicular electric field. It was found that the binding energy of heptazine with embedded Fe atom system decreases as more tensile strain is applied and increases as more electric field strength is applied. Our calculations also predict a band gap at a peak value of 5\% tensile strain but at expense of the structural stability of the system. The band gap opening at 5\% tensile strain is due to distortion in the structure caused by the repulsive effect in the cavity between the lone pairs of edge nitrogen atoms and $\mathrm{d}_{xy}/\mathrm{d}_{x^{2}-y^{2}}$ orbital, hence the unoccupied $\mathrm {p}_z$ orbital is forced to shift towards higher energy. The electronic and magnetic properties of the heptazine with embedded Fe system under perpendicular electric field up to a peak value of 10 V/nm is also well preserved despite obvious buckled structure. Such properties may be desirable for diluted magnetic semiconductors, spintronics, and sensing devices.