First-principles calculations predict the stability and mobility of vacancy defects in niobium perovskite oxynitrides, aiding defect engineering for enhanced photocatalysis.

We propose a local real-space formulation for orbital-free DFT with density dependent kinetic energy functionals and a unified variational framework for computing the configurational forces associated with geometry optimization of both internal atomic positions as well as the cell geometry. The proposed real-space formulation, which involves a reformulation of the extended interactions in elect...

Using electron paramagnetic resonance (EPR), energy levels of the carbon vacancy (V(C)) in 4H-SiC and its negative-U properties have been determined. Combining EPR and deep-level transient spectroscopy we show that the two most common defects in as-grown 4H-SiC--the Z(1/2) lifetime-limiting defect and the EH(7) deep defect--are related to the double acceptor (2-|0) and single donor (0|+) levels...

We present a first-principles study of the molecular vacancy and three distinct molecular interstitial structures in ice Ih. The results indicate that, due to its bonding to the surrounding hydrogen-bond network, the bond-center (Bc) configuration is the favored molecular interstitial in ice Ih. A comparison between the vacancy and the Bc interstitial suggests that the former is the predominant...

Arsenic vacancies in LaFeAsO-derived superconductors are nominally non-magnetic defects. However, we find from a microscopic theory in terms of an appropriately modified Anderson-Wolff model that in their vicinity local magnetic moments form. They can arise because removing an arsenic atom breaks four strong, covalent bonds with the neighboring iron atoms. The moments emerging around an arsenic...

In this paper the boundary conditions for point defect distributions in monocrystalline silicon are investigated. These boundary conditions are established by simple thermodynamic considerations. A circle process is used including vacancy, interstitial and Frenkel pair generation which yields a simple relationship between the vacancy and interstitial equilibrium concentrations at the surface. A...

Vacancy-induced magnetism in graphene bilayers is investigated using spin-polarized density functional theory calculations. One of two graphene layers has a monovacancy. Two atomic configurations for bilayers are considered with respect to the position of the monovacancy. We find that spin magnetic moments localized at the vacancy site decrease by ∼10% for our two configurations, compared with ...

The g value of the excited state associated with the GR1 line is analysed in terms of the Coulson-Kearsley defect-molecule model for the vacancy in diamond. It is shown that the experimentally observed g value is entirely consistent with the expected ’T, level of the model provided quenching by the dynamic Jahn-Teller effect is considered. This quenching is estimated from stress splitting data ...

The electronic behavior of metallic carbon nanotubes under the influence of externally applied electric fields is investigated using the Non-Equilibrium Green’s function method self consistently coupled with three-dimensional (3D) electrostatics. A nearest neighbor tight binding model based on a single pz orbital for constructing the device Hamiltonian is used. The 3D Poisson equation is solved...

Cuprous oxide (Cu2O) is an attractive material for solar energy applications, but its photoconductivity is limited by minority carrier recombination caused by native defect trap states. We examine the creation of trap states by cation vacancies, using first principles calculations based on density functional theory (DFT) to analyze the electronic structure and calculate formation energies. With...