Vibrational properties and Raman spectra of 2‐D octagon‐structure nitrogen

Abstract

We studied the vibrational properties and Raman spectra of two‐dimensional (2‐D) octagon‐structure nitrogen with density functional theory (DFT). There are 10 Raman active modes whose irreducible representations are A1g, B1g, B2g, and Eg. By calculating Raman tensor of each Raman active mode, we obtained polarization angle‐dependent Raman intensities. The results show that B1g and B2g modes can show polarization angle‐dependent Raman intensities when the incident light wave vector is perpendicular to the plane of the nitrogen monolayer, which is different from some other isotropic 2‐D materials. We also discussed polarization angle‐dependent Raman intensities when the incident light wave vector is parallel to the plane of the monolayer. We found that the Raman spectra have seven peaks when the incident light wave vector is perpendicular to the monolayer, while there are four distinct peaks when the incident light wave vector is parallel to the monolayer. Our results will help experimentalists to identify the existence and orientation of octagon‐structure nitrogen monolayer when they are growing it.