Discovering structural, electronic and excitonic properties of bulk, nanostructured and doped C3N4 in diamond- and graphitic-like phases

TL;DR

This study uses density functional theory to compare computational methods for predicting properties of bulk, nanostructured, and doped C3N4 in different phases, focusing on electronic, excitonic, and structural characteristics.

Contribution

It evaluates the accuracy of various DFT functionals and explores the effects of nanostructuring and doping on C3N4's properties, providing insights for photocatalytic applications.

Findings

HSE06-D3 aligns well with experimental and G0W0 data.

Corrugation stabilizes layered structures.

Doping with S modifies electronic and atomic structures.

Abstract

In this systematic density functional theory study, we compare a standard gradient corrected functional (PBE) with a long-range hybrid functional (HSE06), with and without correction for the dispersion forces, relatively to their ability to correctly reproduce structural and electronic properties of different bulk 3D C3N4 phases, encompassing diamond- and graphitic-like models. Corrugation is found to provide further stabilization to the layered structures with all methods. We observe that HSE06-D3 method provides results in good agreement with experimental data and with more sophisticated G0W0 calculations. Based on that, we exploited the method to investigate the nature of the bulk triplet excitons in these C3N4 structures to evaluate the S0-T1 energy difference, the selftrapping triplet exciton energy and the photoluminescence emission energy, since this is a promising vis-light photocatalyst. Nanostructuring (0D and 2D) is another relevant aspect of these materials in practical applications, therefore we have considered the effect of single or multilayer exfoliation or space confinement in nanoparticles. Finally, we also discuss how the introduction of extrinsic dopants (e.g. S atoms) in the nanostructures modifies the atomic and electronic structure.