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

## TL;DR

This study uses density-functional theory to explore how bi-axial tensile strain and electric fields affect the mechanical, electronic, and magnetic properties of Fe-embedded graphitic carbon nitride monolayers, revealing strain-induced band gap tuning.

## Contribution

It provides a detailed first-principles analysis of how external stimuli modulate the properties of Fe-embedded graphitic carbon nitride, highlighting potential applications in spintronics and sensing.

## Key findings

- Band gap appears at 5% tensile strain due to structural distortion.
- Binding energy decreases with tensile strain and increases with electric field.
- Electronic and magnetic properties are stable under electric fields up to 10 V/nm.

## Abstract

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 $\mathrm{Fe}$ atom under bi-axial tensile strain and applied perpendicular electric field. It was found that the binding energy of heptazine with embedded $\mathrm{Fe}$ 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 of Fe atom, hence the unoccupied $\mathrm{p}_z$-orbital is forced to shift towards higher energy. The electronic and magnetic properties of the heptazine with embedded $\mathrm{Fe}$ system under perpendicular electric field up to a peak value of 10 $\mathrm{V/nm}$ is also well preserved despite obvious buckled structure. Such properties may be desirable for diluted magnetic semiconductors, spintronics, and sensing devices.