Exploring the physical properties of Al2O3 under pressure: a study utilizing DFT and equation of state methods

Abstract

Using first-principles density functional theory (DFT) calculations in conjunction with the Murnaghan and Srivastava–Pandey equations of state (EOS), we comprehensively investigate the effect of pressure on the structural, mechanical, thermal, and optical properties of aluminum oxide (Al2O3). Based on structural optimization, we confirm the stability of the corundum phase up to 100 GPa; we find a 10–15% decrease in volume, and the bulk modulus increases from 253 GPa to 330 GPa. The band gap decreases from 9.9 eV to 8.2 eV with rising pressure, as electronic overlap increases and the optical absorption spectrum is likely to be redshifted; the bulk, shear, and Weng's moduli also increase, indicating greater incompressibility. Meanwhile, the thermal conductivity also increases slightly from 30 W/mK to 37.7 W/mK, which can be attributed to the increasing phonon scattering. Optical results reveal a redshift of the absorption edge and a pressure-sensitive refractive index in the 4–6 eV range. The agreement between DFT predictions and experimental results further confirms the model's accuracy. This consistency supports the feasibility of Al2O3 for optoelectronic and geophysical applications at high pressure and provides new insights into its electronic and optical response under pressure.