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

TL;DR

This study uses advanced DFT methods to explore the properties of gold oxides and nanosheets, revealing large spontaneous polarization and unique electronic features with potential catalytic applications.

Contribution

It demonstrates the accurate estimation of band gaps and uncovers spontaneous polarization in Au2O3, including in nanosheets, introducing a novel screening mechanism and phase transition insights.

Findings

Hybrid functional calculations accurately estimate band gaps.

Au2O3 exhibits large spontaneous polarization retained in nanosheets.

Spontaneous polarization vanishes below 0.8 nm thickness, indicating a phase transition.

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.