Sodium-Poor, Hydroxyl-Rich, Defective NaTiO Prepared by γ-Irradiation and Its Enhanced Proton Conductivity.

The use of γ-irradiation to tailor the physicochemical properties of materials is not widely applied to layered alkali metal oxides. Herein, we show that γ-irradiation (up to 400 kGy) of NaTiO leads to a sodium-poor, hydroxyl-rich analogue where the layered structure, plate-like morphology, and textural properties are preserved. The deintercalation of sodium ions modifies the Ti-O bond lengths and expands the unit cell; the latter is supported by density functional theory (DFT) calculations.

The role of native point defects and donor impurities in the electrical properties of ZnSbO: a hybrid density-functional study.

The ceramic material zinc antimony oxide ZnSbO has promising electrical and magnetic properties, making it suitable for various applications such as electrochemical and energy storage. However, the effects of point defects and impurities on its electrical properties have never been revealed. Here, we employ hybrid density-functional calculations to investigate the energetics and electronic properties of native point defects and donor impurities in ZnSbO.

Effects of oxygen pressure on the morphology and surface energetics of β-PbO: insight from DFT calculations.

For over a century, lead dioxide (PbO) has been investigated in lead-acid batteries and extensively utilized in a variety of applications. Identifying the surface properties and equilibrium morphology of β-PbO (rutile phase) particles is mandatory for industrial utilization and surface engineering. Using density-functional calculations within the generalized gradient approximation revised for solids (PBEsol), we investigate a variety of surface properties of β-PbO.

Energetics and optical properties of carbon impurities in rutile TiO.

Titanium dioxide is one of the most promising materials for many applications such as photovoltaics and photocatalysis. Non-metal doping of TiO is widely used to improve the photoconversion efficiency by shifting the absorption edge from the UV to visible-light region. Here, we employ hybrid density-functional calculations to investigate the energetics and optical properties of carbon (C) impurities in rutile TiO.

Energetics of native defects in anatase TiO: a hybrid density functional study.

The energetics and electronic structures of native defects in anatase TiO are comprehensively studied using hybrid density functional calculations. We demonstrate that oxygen vacancies (V) and titanium interstitials (Ti) act as shallow donors, and can form at substantial concentrations, giving rise to free electrons with carrier densities from 10 to 10 cm under oxygen-rich and oxygen-poor conditions, respectively. The titanium vacancies (V), identified as deep acceptors and induced hole carriers, are incapable of fully compensating for the free electrons originating from the donor-type defects at any oxygen chemical potential.

Electronic properties of highly-active Ag3AsO4 photocatalyst and its band gap modulation: an insight from hybrid-density functional calculations.

The electronic structures of highly active Ag-based oxide photocatalysts Ag3AsO4 and Ag3PO4 are studied by hybrid-density functional calculations. It is revealed that Ag3AsO4 and Ag3PO4 are indirect band gap semiconductors. The Hartree-Fock mixing parameters are fitted for experimental band gaps of Ag3AsO4 (1.

Mechanism of photocatalytic activities in Cr-doped SrTiO3 under visible-light irradiation: an insight from hybrid density-functional calculations.

We used hybrid density-functional calculations to clarify the effect of substituting chromium for titanium (Cr(Ti)) on photocatalytic activities of Cr-doped SrTiO(3). A singly negative Cr(Ti)⁻, which is relevant to a lower oxidation state of Cr, is advantageous for the visible light absorption without forming electron trapping centers, while other charge states are inactive for the photocatalytic reaction. Stabilizing the desirable charge state (Cr(Ti)⁻) is feasible by shifting the Fermi level towards the conduction band.

Evidence for native-defect donors in n-type ZnO.

Recent theory has found that native defects such as the O vacancy V(O) and Zn interstitial Zn(I) have high formation energies in n-type ZnO and, thus, are not important donors, especially in comparison to impurities such as H. In contrast, we use both theory and experiment to show that, under N ambient, the complex Zn(I)-N(O) is a stronger candidate than H or any other known impurity for a 30 meV donor commonly found in bulk ZnO grown from the vapor phase. Since the Zn vacancy is also the dominant acceptor in such material, we must conclude that native defects are important donors and acceptors in ZnO.