Theoretical Analysis of Oxygen Diffusion in monoclinic HfO2

2003 ◽  
Vol 786 ◽  
Author(s):  
Minoru Ikeda ◽  
Georg Kresse ◽  
Toshihide Nabatame ◽  
Akira Toriumi
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Atom ◽  
Diffusion Process ◽  
Nearest Neighbor ◽  
Chemical Potential ◽  
Annihilation Process ◽  
Interstitial Oxygen ◽  
Middle Range ◽  
Pair Annihilation ◽  
Charge States

ABSTRACTIn this report, we present the detailed analysis of the interstitial oxygen (O2+, O0, O2-) diffusion in monoclinic HfO2 (hafnia) using the first principles calculations. The interstitial oxygen atom kicks out the oxygen atom at the 3-fold-site and occupies the 3-fold-site. And then the newly kicked-out interstitial oxygen atom jumps to the nearest neighbor site and couples again with the atoms at the crystal sites. This kick-out- mechanism is valid for all charge states of the interstitial oxygen in monoclinic HfO2. In hafnia, the interstitial oxygen atom can take 3 charge states (+2, 0, -2) depending on the chemical potential (Ef), whereas the oxygen-vacancy in hafnia can get +2 or 0 charge state being dependent on Ef. In the lower range of Ef, O2+ and O0 might contribute. In the middle range of Ef, the O2- does not contribute to the diffusion process in hafnia because of the pair annihilation process between O2- and oxygen vacancy (V2+) defect pair. We can simulate such a pair annihilation process in hafnia. In the higher range, O2- might contribute the diffusion process.

scholarly journals Asymmetric dark matter from semi-annihilation

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Avirup Ghosh ◽  
Deep Ghosh ◽  
Satyanarayan Mukhopadhyay
Keyword(s):  
Dark Matter ◽  
Cp Violation ◽  
Chemical Potential ◽  
Unstable State ◽  
Annihilation Process ◽  
Leading Order ◽  
Complex Scalar ◽  
Pair Annihilation ◽  
S Matrix ◽  
Asymmetric Dark Matter

Abstract We show that a general semi-annihilation scenario, in which a pair of dark matter (DM) particles annihilate to an anti-DM, and an unstable state that can mix with or decay to standard model states, can lead to particle anti-particle asymmetry in the DM sector. The present DM abundance, including the CP-violation in the DM sector and the resulting present asymmetry are determined entirely by a single semi-annihilation process at next-to-leading order. For large CP-violation in this process, we find that a nearly complete asymmetry can be obtained in the DM sector, with the observed DM density being dominated by the (anti-)DM particle. The presence of additional pair-annihilation processes can modify the ratio of DM and anti-DM number densities further, if the pair-annihilation is active subsequent to the decoupling of the semi-annihilation. For such a scenario, the required CP-violation for generating the same present asymmetry is generically much smaller, as compared to the scenario with only semi-annihilation present. We show that a minimal model with a complex scalar DM with cubic self-interactions can give rise to both semi- and pair-annihilations, with the required CP-violation generated at one-loop level. We also find that the upper bound on the DM mass from S-matrix unitarity in the purely asymmetric semi-annihilation scenario, with maximal CP-violation, is around 15 GeV, which is much stronger than in the WIMP and previously considered asymmetric DM cases, due to the required large non-zero chemical potential for such asymmetric DM.

scholarly journals Quantitative Evaluations of Hydrogen Diffusivity in V-X (X = Cr, Al, Pd) Alloy Membranes Based on Hydrogen Chemical Potential

Membranes ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 67
Author(s):  
Asuka Suzuki ◽  
Hiroshi Yukawa
Keyword(s):  
Nearest Neighbor ◽  
Chemical Potential ◽  
Hydrogen Permeability ◽  
First Principle ◽  
Hydrogen Diffusivity ◽  
Hydrogen Atoms ◽  
First Principle Calculations ◽  
Blocking Effects ◽  
Pd Alloy ◽  
Quantitative Evaluations

Vanadium (V) has higher hydrogen permeability than Pd-based alloy membranes but exhibits poor resistance to hydrogen-induced embrittlement. The alloy elements are added to reduce hydrogen solubility and prevent hydrogen-induced embrittlement. To enhance hydrogen permeability, the alloy elements which improve hydrogen diffusivity in V are more suitable. In the present study, hydrogen diffusivity in V-Cr, V-Al, and V-Pd alloy membranes was investigated in view of the hydrogen chemical potential and compared with the previously reported results of V-Fe alloy membranes. The additions of Cr and Fe to V improved the mobility of hydrogen atoms. In contrast, those of Al and Pd decreased hydrogen diffusivity. The first principle calculations revealed that the hydrogen atoms cannot occupy the first-nearest neighbor T sites (T1 sites) of Al and Pd in the V crystal lattice. These blocking effects will be a dominant contributor to decreasing hydrogen diffusivity by the additions of Al and Pd. For V-based alloy membranes, Fe and Cr are more suitable alloy elements compared with Al and Pd in view of hydrogen diffusivity.

Oxygen vacancy migration in CSZ using density functional theory

2008 ◽  
Vol 1122 ◽  
Author(s):  
Byeong-Eon Lee ◽  
Dae-Hee Kim ◽  
Yeong-Cheol Kim
Keyword(s):  
Density Functional Theory ◽  
Oxygen Vacancy ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Nearest Neighbor ◽  
Functional Theory ◽  
The Third ◽  
Vacancy Migration ◽  
Neighbor Site ◽  
Formation Energies

AbstractWe studied oxygen migration in calcia-stabilized cubic zirconia (CSZ) using density functional theory. A Ca atom was substituted for a Zr atom in a 2×2×2 ZrO2 cubic supercell, and an oxygen vacancy was produced to satisfy the charge neutrality condition. We found that the formation energies of an oxygen vacancy, as a function of its location with respect to the Ca atom, were varied. The relative formation energies of the oxygen vacancies located at the first-, second-, third-, and fourth-nearest-neighbors were 0.0, −0.07, 0.19, and 0.19 eV, respectively. Therefore, the oxygen vacancy located at the second-nearest-neighbor site of the Ca atom was the most favorable, the oxygen vacancy located at the first-nearest-neighbor site was the second most favorable, and the oxygen vacancies at the third- and fourth-nearest-neighbor sites were the least favorable. We also calculated the energy barriers for the oxygen vacancy migration between oxygen sites. The energy barriers between the first and the second nearest sites, the second and third nearest sites, and the third and fourth nearest sites were 0.11, 0.46, and 0.23 eV, respectively. Therefore, the oxygen vacancies favored the first- and second-nearest-neighbor oxygen sites when they drifted under an electric field.

A LATTICE STATISTICS MODEL DERIVED FROM THE TWO-LAYER ADSORPTION PROBLEM

1965 ◽  
Vol 43 (6) ◽  
pp. 980-985
Author(s):  
D. D. Betts ◽  
D. L. Hunter
Keyword(s):  
Nearest Neighbor ◽  
Chemical Potential ◽  
Physical Adsorption ◽  
Square Lattice ◽  
Lateral Interaction ◽  
Lattice Statistics ◽  
Regular Lattice ◽  
Adsorption Sites ◽  
Layer Adsorption ◽  
Gas Molecules

A model is proposed for the physical adsorption of two layers of gas molecules at the sites of a regular lattice with lateral interaction between nearest-neighbor molecules. The model is more complicated than the two-dimensional Ising model. However, for a particular relation among the three energy parameters and at a particular value of the chemical potential the model simplifies considerably. For the simplified model and a square lattice of adsorption sites, high- and low-temperature series expansions for the specific heat have been obtained and the transition temperature estimated.

Identification of An Interstitial Carbon – Interstitial oxygen Complex in Silicon

1987 ◽  
Vol 104 ◽  
Author(s):  
J. M. Trombetta ◽  
G. D. Watkins
Keyword(s):  
Carbon Atom ◽  
Oxygen Atom ◽  
Lattice Relaxation ◽  
Luminescence Spectra ◽  
Interstitial Oxygen ◽  
Epr Spectrum ◽  
Interstitial Carbon ◽  
Oxygen Complex ◽  
Interaction Tensor ◽  
Carbon Interstitial

ABSTRACTThe Si-G15 EPR spectrum and the 0.79eV “C-line” luminescence spectra in silicon are shown to arise from an interstitial carbon - interstitial oxygen complex. The g-tensor and 13C hyperfine interaction tensor indicate the structure in the vicinity of the carbon atom while stress alignment studies reveal the configuration near the oxygen atom. The pairing of the two impurities leads to a lattice relaxation which serves to stabilize the complex against dissociation.

scholarly journals Fluctuation effects in the pair-annihilation process with Lévy dynamics

2013 ◽  
Vol 88 (1) ◽  
Author(s):  
Ingo Homrighausen ◽  
Anton A. Winkler ◽  
Erwin Frey
Keyword(s):  
Annihilation Process ◽  
Pair Annihilation ◽  
Fluctuation Effects

Theoretical Evaluation of Oxidation Rate of Zr

2013 ◽  
Vol 1535 ◽  
Author(s):  
Yasunori Yamamoto ◽  
Kazunori Morishita ◽  
Hirotomo Iwakiri ◽  
Yasunori Kaneta
Keyword(s):  
Oxygen Vacancy ◽  
Diffusion Process ◽  
Oxidation Rate ◽  
Experimental Fact ◽  
Stress Effect ◽  
Theoretical Evaluation ◽  
Simple Diffusion ◽  
Calculation Results ◽  
And Migration ◽  
Diffusion Coefficient Of Oxygen

ABSTRACTFirst principle calculations were performed to evaluate stress effect on the diffusion process of oxygen vacancy in ZrO2 film, and oxidation rate of Zr was evaluated by solving simple diffusion equations. Our calculation results have indicated that both the vacancy formation and migration energies of ZrO2 increase with increasing compressive applied stress. The energy increase causes a decrease in the diffusion coefficient of oxygen vacancy in ZrO2, leading to a decrease in oxidation rate of Zr. The stress effect on diffusion process may explain the experimental fact that Zr is oxidized in proportion to the cubic root of time.

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