Structural, optoelectronic, excitonic, vibrational, and thermodynamic properties of 1T’-OsO2 monolayer via ab initio calculations

Abstract

To unravel the structural, energetic stability, electronic, optical, excitonic, vibrational, and thermodynamic properties of monoclinic 1A’-OsO2 monolayer, we employed the first-principles calculations based on density functional theory (DFT) within the generalized gradient approximation (GGA) and the HSE06 hybrid functional, considering the norm-conserved pseudopotentials, and a combination of a tight binding plus BSE (TB+BSE) approach for the analysis of optical and excitonic properties at IPA and BSE levels. Our simulations demonstrate that the 1A’-OsO2 monolayer is a structurally and energetically stable semiconductor, and gives us a direct bandgap value, E(Γ→Γ), of 0.304, 0.254, and 1.119 eV, which were obtained through GGA-PBE, GGA-PBE+SOC, and HSE06-level of calculation, respectively. From the excitonic and optical properties, we observe that this system shows a large exciton binding energy of around 0.3 eV for the indirect ground state exciton, displaying an optical bandgap of 0.78 eV. We also show the use of light polarization as a mechanism to control the refractive index. The phonon dispersion and the infrared (IR) and Raman spectra were obtained, with its main peaks being assigned. Lastly, through thermodynamic potentials calculations, the Free energy (F) indicates that the synthesis of the 1A’-OsO2 monolayer would be spontaneous even at low temperatures. All theses properties demonstrate that the 1A’-OsO2 monolayer has potential applications in optoelectronic and thermal devices at the nanoscale.