Functionalities of Au2O, Au2O3, Au2O3-x, and nanosheets, including spontaneous polarization, using DFT and hybrid functional

Abstract

We used density functional theories (DFT) to investigate the properties of Au2O and Au2O3-x (x = 00.08) to reveal their remarkable functionalities. Hybrid functional theories accurately estimate the band gap (Eg) of oxides, and the present hybrid functional calculations determined Eg values of 0.96 eV for Au2O and 2.86 eV for Au2O3, which is >300% of the commonly accepted Eg of Au2O3 (0.85 eV). Moreover, we discovered spontaneous polarization (PS) in Au2O3, which is unusually large and advantageous for catalysis. The PS was retained even in 2-nm-thick Au2O3 nanosheets, similar to hyperferroelectric, generating a potential of 0.6 eV despite screening caused by surface reconstruction, which is a novel screening mechanism. Below a thickness of 0.8 nm, the PS vanished, and inversion symmetry emerged at 0.4 nm, suggesting a new approach to finding a paraelectric phase. Au2O was supersoft under shear distortion.