SiCCSiAntisite Pairs as Dominant Irradiation Induced Defects in p-Type 4H-SiC

2009 ◽  
Vol 615-617 ◽  
pp. 357-360 ◽  
Author(s):  
Uwe Gerstmann ◽  
A.P. Seitsonen ◽  
Francesco Mauri ◽  
Hans Jürgen von Bardeleben
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Paramagnetic Resonance ◽  
Functional Theory ◽  
Radiation Induced ◽  
P Type ◽  
Induced Defects ◽  
Electron Paramagnetic ◽  
Irradiation Induced Defects ◽  
Microscopic Origin

In this work we elucidate the microscopic origin of the dominant radiation induced I-II spectra in p-type doped 4H-SiC. By calculating the electronic g-tensor from first principles in the framework of density functional theory, basal antisite pairs SiCCSi + are shown to give rise to the characteristic anisotropic g-tensors found in the electron paramagnetic resonance (EPR) measurements. Additional central hyperfine (hf) splittings of about 100 MHz due to the SiC antisite nuclei are predicted theoretically and also resolved experimentally. We have, thus, identified antisite pairs as a dominant defect in electron and proton irradiated p-type doped 4H-SiC.

The Interplay of manganese and nitrate in hydroxyapatite nanoparticles as revealed by pulsed EPR and DFT

2015 ◽  
Vol 17 (31) ◽  
pp. 20331-20337 ◽  
Author(s):  
Marat Gafurov ◽  
Timur Biktagirov ◽  
Georgy Mamin ◽  
Elena Klimashina ◽  
Valery Putlayev ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Hydroxyapatite Nanoparticles ◽  
Paramagnetic Resonance ◽  
Functional Theory ◽  
Pulsed Epr ◽  
Pulsed Electron Paramagnetic Resonance ◽  
Electron Paramagnetic ◽  
Oppositely Charged

The interplay of oppositely charged substitutions in the structure of hydroxyapatite nanopowders is investigated by pulsed electron paramagnetic resonance and ab initio density functional theory calculations.

scholarly journals DFT Protocol for EPR Prediction of Paramagnetic Cu(II) Complexes and Application to Protein Binding Sites

2018 ◽  
Vol 4 (4) ◽  
pp. 55 ◽  
Author(s):  
Giuseppe Sciortino ◽  
Giuseppe Lubinu ◽  
Jean-Didier Maréchal ◽  
Eugenio Garribba
Keyword(s):  
Binding Sites ◽  
Density Functional ◽  
Computational Procedure ◽  
Paramagnetic Resonance ◽  
Functional Theory ◽  
Protein Binding Sites ◽  
The Mean ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

With the aim to provide a general protocol to interpret electron paramagnetic resonance (EPR) spectra of paramagnetic copper(II) coordination compounds, density functional theory (DFT) calculations of spin Hamiltonian parameters g and A for fourteen Cu(II) complexes with different charges, donor sets, and geometry were carried out using ORCA software. The performance of eleven functionals was tested, and on the basis of the mean absolute percent deviation (MAPD) and standard deviation (SD), the ranking of the functionals for Az is: B3LYP > B3PW91 ~ B3P86 > PBE0 > CAM-B3LYP > TPSSh > BH and HLYP > B2PLYP > MPW1PW91 > ω-B97x-D >> M06; and for gz is: PBE0 > BH and HLYP > B2PLYP > ω-B97x-D > B3PW91~B3LYP~B3P86 > CAM-B3LYP > TPSSh~MPW1PW91 >> M06. With B3LYP the MAPD with respect to A z exp t l is 8.6% with a SD of 4.2%, while with PBE0 the MAPD with respect to g z exp t l is 2.9% with a SD of 1.1%. The results of the validation confirm the fundamental role of the second order spin-orbit contribution to Az. The computational procedure was applied to predict the values of gz and Az of the adducts formed by Cu(II) with albumin and two fragments of prion protein, 106–126 and 180–193.

Distribution of the unpaired electron in neutral bis(phthalocyaninato) yttrium double-deckers: An experimental and theoretical combinative investigation

2018 ◽  
Vol 22 (01n03) ◽  
pp. 165-172 ◽  
Author(s):  
Xin Chen ◽  
Yuxiang Chen ◽  
Ming Bai ◽  
Chiming Wang ◽  
Dongdong Qi ◽  
...  
Keyword(s):  
Unpaired Electron ◽  
Density Functional ◽  
Population Distribution ◽  
Experimental Methods ◽  
Molecular Structures ◽  
Paramagnetic Resonance ◽  
Functional Theory ◽  
Double Decker ◽  
Tetrapyrrole Chromophores ◽  
Electron Paramagnetic

The location of the unpaired electron in neutral bis(phthalocyaninato) yttrium double-decker complexes, with different substituents, has been studied on the basis of both experimental methods and density functional theory (DFT) calculations over the molecular structures, atomic charges, electronic absorption, infrared spectra, and electron paramagnetic resonance. The results reveal the location of the unpaired electron mainly on the carbon atoms of both tetrapyrrole chromophores with the population distribution obviously affected by the peripheral substituents.

Radiation-induced defects in montebrasite: An electron paramagnetic resonance study of O – hole and Ti3+ electron centers

2020 ◽  
Vol 105 (7) ◽  
pp. 1051-1059
Author(s):  
José R. Toledo ◽  
Raphaela de Oliveira ◽  
Lorena N. Dias ◽  
Mário L.C. Chaves ◽  
Joachim Karfunkel ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Irradiation ◽  
Color Centers ◽  
Hydroxyl Groups ◽  
Γ Irradiation ◽  
Paramagnetic Resonance ◽  
Radiation Induced ◽  
Induced Defects ◽  
Electron Paramagnetic ◽  
Hole Centers

Abstract Montebrasite is a lithium aluminum phosphate mineral with the chemical formula LiAlPO4(Fx,OH1–x) and considered a rare gemstone material when exhibiting good crystallinity. In general, montebrasite is colorless, sometimes pale yellow or pale blue. Many minerals that do not have colors contain hydroxyl ions in their crystal structures and can develop color centers after ionization or particle irradiation, examples of which are topaz, quartz, and tourmaline. The color centers in these minerals are often related to O− hole centers, where the color is produced by bound small polarons inducing absorption bands in the near UV to the visible spectral range. In this work, colorless montebrasite specimens from Minas Gerais state, Brazil, were investigated by electron paramagnetic resonance (EPR) for radiation-induced defects and color centers. Although γ irradiation (up to a total dose of 1 MGy) did not visibly modify color, a 10 MeV electron irradiation (80 MGy) induced a pale greenish-blue color. Using EPR, O− hole centers were identified in both γ- or electron-irradiated montebrasite samples showing superhyperfine interactions with two nearly equivalent 27Al nuclei. In addition, two different Ti3+ electron centers were also observed. From the γ irradiation dose dependency and thermal stability experiments, it is concluded that production of O− hole centers is limited by simultaneous creation of Ti3+ electron centers located between two equivalent hydroxyl groups. In contrast, the concentration of O− hole centers can be strongly increased by high-dose electron irradiation independent of the type of Ti3+ electron centers. From detailed analysis of the EPR angular rotation patterns, microscopic models for the O− hole and Ti3+ electron centers are presented, as well as their role in the formation of color centers discussed and compared to other minerals.

Redox Levels of a closo-Osmaborane: A Density Functional Theory, Electron Paramagnetic Resonance and Electrochemical Study

2015 ◽  
Vol 54 (9) ◽  
pp. 4292-4302 ◽  
Author(s):  
Alexandr N. Simonov ◽  
John F. Boas ◽  
Melissa A. Skidmore ◽  
Craig M. Forsyth ◽  
Elena Mashkina ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electron Paramagnetic Resonance ◽  
Density Functional ◽  
Electrochemical Study ◽  
Paramagnetic Resonance ◽  
Functional Theory ◽  
Electron Paramagnetic
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