Electronic, Elastic, Piezoelectric, and Infrared Properties of 2D Phosphorus Oxynitride by First Principles

Abstract

Bulk phosphorus oxynitride (PON), isoelectronic with SiO2, is confirmed to have many polymorphs as the latter. However, its 2D counterparts have not been studied. In this work, crystal structure exploration and property study are performed on 2D PON with the help of first‐principle calculation. Three 2D PON sheets are found with thermal, dynamical, and mechanical stability and all of them can be viewed as oxygen‐doped known 2D γ phosphorus nitride (γ‐PN). In the studies, it is indicated that they are indirect bandgap materials with gap values larger than 3 eV. The situations of orbital hybridization are discussed and their bonding properties are analyzed. Infrared vibrational spectra of these 2D materials are simulated and the vibrational modes at the Brillouin center are assigned by the factor group analysis. The reasons for the disappearance of some infrared peaks in the simulated spectra are revealed based on the calculated Born effective charges and vibrational eigenvectors. Their piezoelectric stress tensors are computed via density‐functional perturbation method and the piezoelectric strain tensors are also deduced via the calculated elastic constants. In the results, it is uncovered that these 2D PON sheets have considerably greater piezoelectric coefficients than the primitive 2D γ‐PN, which make them promising for nanopiezoelectric use.