A first-principles study of native point defects in monoclinic, cubic, two different tetragonal, and five orthorhombic phases hafnia (HfO2) is presented. They include vacancy tri-coordinated tetra-coordinated oxygen, metal vacancy, interstitial metal, oxygen. Defect formation energy, trap depth, relaxation energy upon optical excitation are listed. The depth oxygen vacancies shows little variat...

Our results validate the use of independent DFT predicted BE shifts for defect identification and constraining ambient pressure XPS observations for Me-Nx moieties in pyrolyzed carbon based ORR electrocatalysts. This supports the understanding of such catalysts as vacancy-and-substitution defects in a graphene-like matrix.

A multilength scale method based on asymptotic expansion homogenization (AEH) is developed to compute minimum energy configurations of ensembles of atoms at the fine length scale and the corresponding mechanical response of the material at the coarse length scale. This multiscale theory explicitly captures heterogeneity in microscopic atomic motion in crystalline materials, attributed, for exam...

Electron paramagnetic resonance (EPR) was used to study high-purity semi-insulating 4H-SiC irradiated with 2 MeV electrons at room temperature. The EPR signal of the EI4 defect was found to be dominating in samples irradiated and annealed at ~750°C. Additional large-splitting Si hyperfine (hf) lines and also other C and Si hf structures were observed. Based on the observed hf structures and ann...

Ferroelectric 1 mol.% La3+ and 0.5 mol.% Fe3+ codoped Pb[Zr0 54Ti0 46]O3 ceramics were studied by means of multifrequency electron paramagnetic resonance (EPR) spectroscopy. The obtained results prove that iron is incorporated at the [Zr,Ti]-site, acting as an acceptor and building a charged (Fe Zr,Ti V O ) defect dipole with a directly coordinated oxygen vacancy for partial charge compensation...

Point defects play an important role in determining the structural stability and mechanical behavior of intermetallic compounds. To help quantitatively understand the point defect properties in these compounds, we developed PyDII, a Python program that performs thermodynamic calculations of equilibrium intrinsic point defect concentrations and extrinsic solute site preferences in intermetallics...