Positron annihilation spectroscopy, when combined with highquality supporting modeling of positron states and annihilation in matter, is a powerful tool for detailed defect identification of vacancy-type defects in semiconductors and oxides. Here we demonstrate that the Doppler broadening of the positron annihilation radiation is a very sensitive means for observing the oxygen environment aroun...

Bouquet-like hierarchical Bi2O3 photocatalyst materials with high-density surface oxygen vacancy are synthesized via a hydrothermal method by the synergetic control of NaOH and a polyvinyl alcohol (PVA) stabilizer. The OH(-) ion addition led to the formation of more relaxed PVA macromolecular clusters, as a result, a thinner PVA film was formed, the species adsorbed on the surface of the produc...

Atomistic thermodynamic calculations are performed in order to examine the energetic% of self-diffusion in GaAs. An energetic assessment of the activation enthalpy of the saddle-point configuration of various modes of vacancy self-diffusion indicates second-nearest-neighbor hopping to be the energetically most favorable mechanism if vacancies are available in equilibrium concentrations. An asse...

Isolated point defects possessing a high spin ground state and below-band-gap excitation may play a key role in realizing solid state quantum bits in semiconductors which are the basic building blocks of quantum computers. The silicon vacancy in silicon carbide provides these features, making it a feasible candidate in this special and emerging field of science. However, the exact nature of the...

The atomic level mechanism of incorporation of Zn(2+) into hydroxyapatite (HAp), which is a potential dopant to promote bone formation, was investigated, based on first principles total energy calculations and experimental X-ray absorption near edge structure (XANES) analyses. It was found that Zn(2+)-doped HAp tends to have a Ca-deficient chemical composition and substitutional Zn(2+) ions are...

1. Introduction In the presence of interstitial H atoms, the concentration of M-atom vacancies is enhanced dramatically, forming a defect structure containing superabundant vacancies (SAVs). The diffusivity of M atoms is enhanced accordingly. Physically, these phenomena are the result of the lowering of the formation energy of a vacancy by trapping H atoms [1, 2]. A Monte Carlo calculation on t...

Resolving the atomic structure of the surface of ice particles within clouds, over the temperature range encountered in the atmosphere and relevant to understanding heterogeneous catalysis on ice, remains an experimental challenge. By using first-principles calculations, we show that the surface of crystalline ice exhibits a remarkable variance in vacancy formation energies, akin to an amorphou...

We study the mechanism of vacancy migration and phase transitions of 3D crystalline colloidal arrays (CCA) using Langevin dynamics simulations. We calculate the self-diffusion coefficient of the colloid particles and the diffusion constant for vacancies as a function of temperature and DLVO potential parameters. We investigate the phase behavior of several systems with different interaction pot...

The temperature dependence of the nuclear spin-lattice relaxation rate R\ of Sc has been measured in scandium dihydrides and dideuterides. These data are satisfactorily accounted for by two contributions to /?,, R]e due to conduction electrons, and R]Q due to quadrupo le interaction fluctuations resulting f rom vacancy diffusion on the hydrogen (deuter ium) sublattice. Describing these fluctuat...

We report on the detection of electric field-induced second harmonic generation (EFISHG) from the anode interfaces of reduced and oxidized Fe-doped SrTiO₃ (Fe:STO) single crystals. For the reduced crystal, we observe steady enhancements of the susceptibility components as the imposed dc-voltage increases. The enhancements are attributed to a field-stabilized electrostriction, leading to Fe:Ti-O...