Novel inorganic graphenylene based on scandium nitride: Stability, mechanical, and electronic properties

This study introduces a novel two-dimensional inorganic graphenylenelike monolayer, scandium nitride (IGP-ScN), and examines its stability and functional properties using density functional theory (DFT) simulations. Phonon dispersion analysis and ab initio molecular dynamics in the NVT ensemble (300--900 K) confirm both dynamical and thermal robustness. At the PBE level, electronic structure calculations indicate an indirect band gap at $M\ensuremath{\rightarrow}\mathrm{\ensuremath{\Gamma}}$. The Bethe-Salpeter equation solution reveals an indirect excitonic ground state and an optical gap at 1.96 eV, indicating a large exciton binding energy (646 meV) and a pronounced excitonic red shift. The monolayer satisfies the Born-Huang stability criteria and demonstrates an essentially isotropic in-plane elastic response, with a Young's modulus of approximately 52 N/m, a shear modulus of approximately 17 N/m, and a Poisson's ratio of approximately 0.51. The lattice thermal conductivity is low, ranging from 0.09 W/(m K) at 300 K to 0.03 W/(m K) at 900 K. Although the undoped structure has low figure-of-merit (zT) values, doping at elevated temperatures can improve performance, with electron doping more effective than hole doping. Power conversion efficiency (PCE) results show Shockley-Queisser limit efficiencies of $10.58%$ at the independent particle approximation level and $23.19%$ at the Bethe-Salpeter level, with the latter enhanced by the excitonic redshift, which reduces the optical band gap from 2.42 to 1.96 eV. These findings may encourage further investigation of new III--V semiconductors and novel inorganic lattices by both experimental and theoretical researchers.