Comment on 'Erratum: 'Two-dimensional porous graphitic carbon nitride C6N7 monolayer: First-principles calculations' [Appl. Phys. Lett. 119, 142102 (2021)]'

TL;DR

This paper critiques previous DFT studies on the elastic properties of the C6N7 monolayer, correcting errors and providing new calculations that confirm its isotropic in-plane elasticity.

Contribution

It corrects prior inaccuracies in elastic constant calculations and offers new DFT and machine learning results for C6N7 monolayer's elastic properties.

Findings

Corrected elastic constants: C11=286 GPa, C12=73 GPa, C66=107 GPa

In-plane Young's modulus of 267 GPa

C6N7 monolayer exhibits isotropic elasticity

Abstract

Recently, Bafekry et al. [Appl. Phys. Lett. 120, 189901 (2022)] reported their density functional theory (DFT) results on the elastic constants of C6N7 monolayer. They predicted non-zero elastic constants along the out-of-plane direction for a single-layered material, which contradicts with basic physics of the stiffness tensor for plane stress condition. Moreover, in their work Young's modulus is erroneously calculated. On the basis of DFT calculations, herein we predicted the C11, C12 and C66 of the C6N7 monolayer to be 286, 73 and 107 GPa, respectively, equivalent with an in-plane Youngs modulus of 267 GPa. Using DFT calculations and a machine learning interatomic potential, we also show that C6N7 monolayer shows isotropic elasticity.