scholarly journals The Interstitial Carbon–Dioxygen Center in Irradiated Silicon

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1005
Author(s):  
Marianna S. Potsidi ◽  
Navaratnarajah Kuganathan ◽  
Stavros-Richard G. Christopoulos ◽  
Alexander Chroneos ◽  
Theoharis Angeletos ◽  
...  
Keyword(s):  
Density Functional ◽  
Dipole Interaction ◽  
Energy Structure ◽  
Potential Candidate ◽  
Interstitial Oxygen ◽  
Local Vibrational Mode ◽  
Ir Studies ◽  
Oxygen Interstitial ◽  
A Value ◽  
Carbon Interstitial

We investigated, experimentally as well as theoretically, defect structures in electron irradiated Czochralski-grown silicon (Cz-Si) containing carbon. Infrared spectroscopy (IR) studies observed a band at 1020 cm−1 arisen in the spectra around 300 °C. Its growth occurs concomitantly with the decay out of the well-known vacancy-oxygen (VO) defect, with a Local Vibrational Mode (LVM) at 830 cm−1 and carbon interstitial-oxygen interstitial (CiOi) defect with a LVM at 862 cm−1, in silicon (Si). The main purpose of this work is to establish the origin of the 1020 cm−1 band. One potential candidate is the carbon interstitial-dioxygen (CiO2i) defect since it is expected to form upon annealing out of the CiOi pair. To this end, systematic density functional theory (DFT) calculations were used to predict the lowest energy structure of the (CiO2i) defect in Si. Thereafter, we employed the dipole–dipole interaction method to calculate the vibrational frequencies of the structure. We found that CiO2i defect has an LVM at ~1006 cm−1, a value very close to our experimental one. The analysis and study of the results lead us to tentatively correlate the 1020 cm−1 band with the CiO2i defect.

First-principles study of oxygen incorporation and migration mechanisms in Ti2AlC

2009 ◽  
Vol 24 (10) ◽  
pp. 3190-3196 ◽  
Author(s):  
Ting Liao ◽  
Jingyang Wang ◽  
Meishuan Li ◽  
Yanchun Zhou
Keyword(s):  
Density Functional ◽  
Atomic Layer ◽  
Interstitial Site ◽  
Interstitial Oxygen ◽  
Oxygen Incorporation ◽  
Oxygen Interstitial ◽  
Chemical Potentials ◽  
Layer I ◽  
And Migration ◽  
And Diffusion

We performed density-functional calculations of oxygen incorporation and diffusion in layered Ti2AlC for a range of intrinsic- and impurity-element chemical potentials. In view of the thermal equilibrium coexistence between oxygen-dissolved Ti2AlC and the oxide scale, a thermodynamic scheme is presented that allows the comparison of the relative stability of oxygen defects in different exterior environments. The calculations show that the oxygen atom favors substitution on carbon lattice sites (OC) under oxygen-lean conditions and high temperatures, whereas the occurrence of an oxygen interstitial in the aluminum atomic layer (IO-tri) becomes more preferential in an oxygen-rich atmosphere and low temperatures. Interstitial oxygen (IO-tri) diffusion via a metastable interstitial site (IO-oct) has a comparatively low migration energy. The substitutional oxygen defect (OC) diffuses by exchanging with neighboring carbon vacancy, which needs a relatively high diffusion barrier.

DEFECT-ORIGIN AND STABILITY OF VISIBLE EMISSION IN ZnO NANOPILLARS

2012 ◽  
Vol 05 (03) ◽  
pp. 1240001 ◽  
Author(s):  
XIAOYONG XU ◽  
ZHULIN JIN ◽  
CHUNXIANG XU ◽  
JIYUAN GUO ◽  
ZENGLIANG SHI ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Density Functional ◽  
Photoluminescence Property ◽  
Green Emission ◽  
Interstitial Oxygen ◽  
Vapor Phase Transport ◽  
Violet Emission ◽  
Oxygen Interstitial ◽  
Zinc Interstitial ◽  
Vapor Phase Transport Method

ZnO nanopillars with the strong violet photoluminescence were fabricated via the vapor-phase transport method. The annealing effect on photoluminescence property was probed to indicate the defect-origins of visible emissions and their thermodynamic stabilities. Moreover, the electron structures of ZnO with zinc interstitial, oxygen vacancy and oxygen interstitial were calculated based on the density functional theory. Three important points were demonstrated: zinc interstitial as an instable donor determines the violet emission and the concentration of free carriers; oxygen vacancy as a steady donor is responsible for the green emission; and oxygen interstitial may induce the yellow-green emission and lead to the red-shift and asymmetry of photoluminescence spectra. These results are beneficial to understand the defect-origins of the visible emissions and their stabilities in ZnO nanostructures, and extending optical and electronic applications.

FIRST PRINCIPLE CALCULATION OF ELECTRONIC BAND STRUCTURE AND OPTICAL PROPERTIES OF KIO3

2009 ◽  
Vol 23 (10) ◽  
pp. 2405-2412
Author(s):  
HARUN AKKUS ◽  
BAHATTIN ERDINC
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
Functional Methods ◽  
A Value ◽  
Direct Band

The electronic band structure and optical properties of the ferroelectric single crystal KIO 3 have been investigated using the density functional methods. The calculated band structure for KIO 3 evidences that the crystal has a direct band gap with a value of 2.83 eV. The structural optimization has been performed. The real and imaginary parts of dielectric function, energy-loss function for volume and surface, and refractive index are calculated along the crystallographic axes.

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.

Conformation and electronic structure of Carbidopa. A QM/MD study

2016 ◽  
Vol 15 (01) ◽  
pp. 1650002
Author(s):  
Ghader M. Sukker ◽  
Nuha Wazzan ◽  
Ashour Ahmed ◽  
Rifaat Hilal
Keyword(s):  
Density Functional ◽  
Minimum Energy ◽  
Geometry Optimization ◽  
Md Simulations ◽  
Energy Structure ◽  
Functional Theory ◽  
Conformational Preferences ◽  
The Density Functional Theory ◽  
Quantum Chemical Topology ◽  
Bonding Characteristics

Carbidopa (CD) is a drug used in combination with L-dopa (LD) in treatment of Parkinson’s disease (PD). CD is an inhibitor for enzyme decarboxylase, yet its mode of action is not entirely known although it is believed to involve enzyme shape recognition. The present work attempts to investigate the conformational preferences of CD. Tight geometry optimization at the density functional theory (DFT)/B3LYP/6-311[Formula: see text]G** level of theory has been carried out. The shallow nature of the potential energy surface (PES) and the presence of several local minima within a small energy range necessitate the launching of DFT-based molecular dynamics (MD) simulations. Two MD experiments were submitted for 35,000 points each. The complete trajectory in time domain of 10.5 ps is analyzed and discussed. The global minimum energy structure of CD is localized and identified by subsequent frequency calculations. The quantum theory of atom in molecules (QTAIMs) is used to extract and compare the quantum chemical topology features of the electron density distribution in CD and LD. Bonding characteristics are analyzed and discussed within the natural bond orbital (NBO) framework.

scholarly journals Atomic, electronic and magnetic structure of an oxygen interstitial in neutron-irradiated Al2O3 single crystals

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
V. Seeman ◽  
A. Lushchik ◽  
E. Shablonin ◽  
G. Prieditis ◽  
D. Gryaznov ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Single Crystals ◽  
Density Functional ◽  
Magnetic Moments ◽  
Atomic Charges ◽  
Interstitial Oxygen ◽  
Absorption Bands ◽  
Magnetic Field Rotation ◽  
Formal Charge ◽  
Radiation Induced

Abstract A single radiation-induced superoxide ion $$O_{2}^{ - }$$ O 2 - has been observed for the first time in metal oxides. This structural defect has been revealed in fast-neutron-irradiated (6.9×1018n/cm2) corundum (α-Al2O3) single crystals using the EPR method. Based on the angular dependence of the EPR lines at the magnetic field rotation in different planes and the determined g tensor components, it is shown that this hole-type $$O_{2}^{ - }$$ O 2 - center (i) incorporates one regular and one interstitial oxygen atoms being stabilized by a trapped hole (S = 1/2), (ii) occupies one oxygen site in the (0001) plane being oriented along the a axis, and (iii) does not contain any other imperfection/defect in its immediate vicinity. The thermal stepwise annealing (observed via the EPR signal and corresponding optical absorption bands) of the $$O_{2}^{ - }$$ O 2 - centers, caused by their destruction with release of a mobile ion (tentatively the oxygen ion with the formal charge −1), occurs at 500–750 K, simultaneously with the partial decay of single F-type centers (mostly with the EPR-active F+ centers). The obtained experimental results are in line with the superoxide defect configurations obtained via density functional theory (DFT) calculations employing the hybrid B3PW exchange-correlation functional. In particular, the DFT calculations confirm the $$O_{2}^{ - }$$ O 2 - center spin S = 1/2, its orientation along the a axis. The $$O_{2}^{ - }$$ O 2 - center is characterized by a short O–O bond length of 1.34 Å and different atomic charges and magnetic moments of the two oxygens. We emphasize the important role of atomic charges and magnetic moments analysis in order to identify the ground state configuration.

Searching for a new family of high energy explosives by introducing N atoms, N-oxides, and NO2 into a cage adamantane

2016 ◽  
Vol 94 (8) ◽  
pp. 667-673 ◽  
Author(s):  
Dong Xiang ◽  
Hao Chen ◽  
Weihua Zhu ◽  
Heming Xiao
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Design Strategy ◽  
High Energy ◽  
Impact Sensitivity ◽  
Lower Sensitivity ◽  
Detonation Properties ◽  
Potential Candidate ◽  
Functional Theory ◽  
New Family

A design strategy that including N atoms, N-oxides, and nitro groups into a cage azaadamantane at the same time was used to design 10 polyazaoxyadamantanes (PAOAs) and eight polynitroazaoxyadamantanes (PNTAOAs). First, four stable azaadamantanes were built by replacing the tertiary C atoms of an adamantane with N atoms. Then, 10 PAOAs were designed by introducing one to four N-oxides into the four azaadamantanes. After that, eight PNTAOAs were formed when the H atoms of four N-oxide-substituted azaadamantanes were replaced with different numbers of nitro groups. Finally, their heats of formation, densities, detonation properties, and impact sensitivity were estimated by using density functional theory. Among the eight PNTAOAs, seven compounds had better detonation performances than CL-20, the outstanding, novel, high-energy, and relatively insensitive cage explosive. Two compounds had higher detonation performance and lower sensitivity than CL-20 and HMX, suggesting that their overall performances are outstanding and they may be considered as the potential candidate of high-energy explosives.

Theoretical Insights into the Role of Water Molecule in The Aqueous/Cu(111) Interface during Corrosion Pathway

2014 ◽  
Vol 19 (4) ◽  
pp. 235-240
Author(s):  
Jun Hu ◽  
Xiao-yong Fan ◽  
Chao-Ming Wang
Keyword(s):  
Water Molecule ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Adsorbed Water ◽  
Dipole Interaction ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Adsorbed Water Molecule ◽  
The One

The absorption and possible reaction paths during corrosion have been systematically identified at the molecular level by us-ing density functional theory calculations. The results show that the co-adsorbed water molecule has a two-fold impact on the corrosive kinetics process. The one is the solvation effect, where water molecule affects the various reactions through ion dipole interaction, without bond fracture and formation. Another is the H-transfer mediator, where the bond of co-adsorbed water molecule breaks and regenerates in order to transfer hydrogen atoms.

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