Ab-initio study of the influence of pressure on the electronic, optical and thermodynamic properties of SrGd2O4 spinel

Abstract

This study uses DFT calculations to investigate the effects of pressure on the electronic, optical, and thermodynamic properties of SrGd₂O₄. The pressure reduces the band gap energy of SrGd₂O₄ from 4.41 eV at 0Pa to 2.23 eV at 35 GPa, highlighting significant changes in its optoelectronic properties. Moreover, as pressure increases to 35 GPa, significant changes are observed in the imaginary part of the dielectric tensor, which doubles from 1.02 to 3.92 at 4.3 eV, indicating enhanced light absorption. The optical conductivity rises from 680 to 2800 (Ω cm)⁻¹, and the absorption coefficient increases from 12 to 42 × 10⁴/cm. The complex refractive index also varies from 2 to 2.6. Reflectivity improves from 0.12 to 0.21 at 4.2 eV. These findings illustrate the potential for fine-tuning the optical properties of the material through pressure, offering valuable insights for applications in photonics and optoelectronics. Thermodynamically, as pressure is applied, the crystal lattice of the material is compressed, which alter the vibrational modes of the atoms. This compression often leads to an increase in the vibrational frequencies of the phonons, leading the specific heat capacity peak to shift to higher temperatures (from 120 K at 0Pa to 170 K at 36 GPa).