Novel two-dimensional Janus YMN (M= I, Br and N= Cl, Br) monolayers

Based on density functional theory, we have investigated the structural, electronic, mechanical, and dynamic stability properties of novel Janus YMN monolayers (M= I, Br and N= Cl, Br). The calculated cohesive energies for these monolayers are −4.13 eV/atom, −3.95 eV/atom, and −4.38 eV/atom, respectively. Upon calculating exfoliation energy values of 0.23 J/m2, 0.24 J/m2, and 0.22 J/m2 for YICl, YIBr, and YBrCl, respectively, it is suggested that the predicted monolayers can be readily separated from the bulk material through experimental exfoliation. The electronic band structure of these monolayers reveals semiconducting features with an indirect band gap, both with and without the inclusion of spin–orbit coupling (SOC). Additionally, when the hybrid function (HSE06) is used in the absence of SOC, the band gaps of the YICl, YIBr, and YBrCl monolayers are determined to be 0.89 eV, 0.85 eV, and 1.09 eV, respectively. Elastic constants and phonon dispersion calculations indicate the mechanical and dynamic stability of the YICI, YIBr, and YBrCl monolayers. We also confirm that the ab initio molecular dynamics examination reveals no observable structural deformation or broken bonds within the structures. While demonstrating similar optical properties based on the dielectric constant results, the calculated imaginary part of the dielectric function corresponds to the vacuum ultraviolet (VUV) region of the electromagnetic spectrum. Overall, the findings suggest potential applications of the novel Janus YMN (M= I, Br and N= Cl, Br) monolayers in optoelectronics.