ENERGETICS OF VHg-RELATED DEFECTS IN As-DOPED HgCdTe

2013 ◽  
Vol 27 (30) ◽  
pp. 1350178
Author(s):  
H. DUAN ◽  
Y. Z. DONG ◽  
Z. P. LIN ◽  
X. ZHANG ◽  
Y. HUANG ◽  
...  
Keyword(s):  
Defect Formation ◽  
Annealing Treatment ◽  
Binding Energies ◽  
First Principles Calculations ◽  
Activation Model ◽  
Chemical Potentials ◽  
Postgrowth Annealing ◽  
Shallow Acceptors ◽  
Formation Energies ◽  
Arsenic Vacancy

Arsenic-doped HgCdTe usually exhibits compensated n-type conductivity, which is ambiguously attributed to isolated vacancies (V Hg ) or arsenic-vacancy complexes ( As Hg – V Hg and As Hg –2V Hg ). Our first-principles calculations clarified the correlation of these V Hg -related defects with the carrier compensation in As -doped HgCdTe by calculating the defect formation energies, as a function of atomic/electron chemical potentials. Under n-type condition, the lowest formation energy defect is found to be the As Hg donor followed by the V Hg acceptor, leading to a compensated n-type material. The arsenic-vacancy complexes are shallow acceptors but their high formation energies render them unlikely to be the compensating candidates. Their large binding energies, however, allow us to predict that the formation of the As Hg –2V Hg complex defect will be enhanced under postgrowth annealing treatment, in agreement with the arsenic activation model by Berding et al. [J. Electron. Mater.27, 605 (1998)].

New Pt-based Superalloy System Designed from First Principles

2008 ◽  
Vol 1128 ◽  
Author(s):  
Vsevolod I. Razumovskiy ◽  
Eyvaz I. Isaev ◽  
Andrei V. Ruban ◽  
Pavel A. Korzhavyi
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Defect Formation ◽  
Alloy System ◽  
First Principles Calculations ◽  
Phonon Spectra ◽  
Ultrahigh Temperature ◽  
New Generation ◽  
Formation Energies ◽  
Temperature Applications

AbstractPt-Sc alloys with the γ-γ′ microstructure are proposed as a basis for a new generation of Pt-based superalloys for ultrahigh-temperature applications. This alloy system was identified on the basis of first-principles calculations. Here we discuss the prospects of the Pt-Sc alloy system on the basis of calculated elastic properties, phonon spectra, and defect formation energies.

Computational study of Mg insertion into amorphous silicon: advantageous energetics over crystalline silicon for Mg storage

2013 ◽  
Vol 1540 ◽  
Author(s):  
Fleur Legrain ◽  
Oleksandr I. Malyi ◽  
Teck L. Tan ◽  
Sergei Manzhos
Keyword(s):  
Density Functional ◽  
Nearest Neighbor ◽  
Defect Formation ◽  
Crystalline Silicon ◽  
Computational Study ◽  
Binding Energies ◽  
Functional Theory ◽  
Wide Range ◽  
Insertion Sites ◽  
Formation Energies

ABSTRACTWe show in a theoretical density functional theory study that amorphous Si (a-Si) has more favorable energetics for Mg storage compared to crystalline Si (c-Si). Specifically, Mg and Li insertion is compared in a model a-Si simulation cell. Multiple sites for Mg insertion with a wide range of binding energies are identified. For many sites, Mg defect formation energies are negative, whereas they are positive in c-Si. Moreover, while clustering in c-Si destabilizes the insertion sites (by about 0.1/0.2 eV per atom for nearest-neighbor Li/Mg), it is found to stabilize some of the insertion sites for both Li (by up to 0.27 eV) and Mg (by up to 0.35 eV) in a-Si. This could have significant implications on the performance of Si anodes in Mg batteries.

First Principles Study of Point Defects in Uranium Dioxide

2007 ◽  
Vol 561-565 ◽  
pp. 1971-1974 ◽  
Author(s):  
Ying Chen ◽  
Misako Iwasawa ◽  
Yasunori Kaneta ◽  
Toshiharu Ohnuma ◽  
Hua Yun Geng ◽  
...  
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Defect Formation ◽  
Lattice Relaxation ◽  
Atomic Displacement ◽  
Grain Structure ◽  
First Principles Calculations ◽  
Fine Grain ◽  
Unit Cells ◽  
Formation Energies

To clarify the origin of a characteristic fine grain structure formed under the high burn-up of the nuclear fuel, the comprehensive first-principles calculations for UO2 containing various types of point defect have been performed by the PAW-GGA+U with lattice relaxation for supercells containing 1, 2 and 8 unit cells of UO2. The electronic structure, the atomic displacement and the defect formation energies of defective systems are obtained, and the effects of supercell size on these properties are discussed. Based on this relatively high precise self-consistent formation energies dataset, thermodynamic properties of various types of point defects in UO2 are further investigated in the framework of the point defects model.

Calculation of defect formation energies in UO2

2014 ◽  
Vol 1645 ◽  
Author(s):  
Julia Wiktor ◽  
Emerson Vathonne ◽  
Michel Freyss ◽  
Gérald Jomard ◽  
Marjorie Bertolus
Keyword(s):  
Phase Diagram ◽  
Defect Formation ◽  
Experimental Phase ◽  
Experimental Phase Diagram ◽  
Ionic System ◽  
Chemical Potentials ◽  
Charge States ◽  
Image Position ◽  
Formation Energies

ABSTRACTWe present a physically justified formalism for the calculation of defect formation energies in UO2. The accessible ranges of chemical potentials of the two components U and O are calculated using the U-O experimental phase diagram and a constraint on the formation energies of vacancies. We then apply this formalism to the DFT+U investigation of the monovacancies and monointerstitials in UO2.The results of the most stable charge states of these defects are consistent with a strongly ionic system. Calculations predict similarly low formation energies for $V_U^{4 - }$ and $I_O^{2 - }$ in hyperstoichiometric UO2.

First-principles calculations of intrinsic defects in the p-type semiconductor CuAlO2

2010 ◽  
Vol 88 (12) ◽  
pp. 927-932 ◽  
Author(s):  
Dan Huang ◽  
Yuanming Pan
Keyword(s):  
First Principles ◽  
Defect Formation ◽  
First Principles Calculations ◽  
Image Charge ◽  
Intrinsic Defects ◽  
Type Conductivity ◽  
The Poor ◽  
Type Semiconductor ◽  
P Type ◽  
Formation Energies

Intrinsic defects, including vacancies at the Cu and Al sites (VCu and VAl), substitutional Cu at the Al site (CuAl), and interstitial O (Oi), have been proposed to be responsible for the p-type conductivity in CuAlO2. We have investigated the formation energies of these and other intrinsic defects in CuAlO2 using GGA+U calculations. Our results support previous studies that the potential alignment and image charge correction are required in the calculation of defect formation energies by using the supercell approach. In CuAlO2, these p-type defects (VCu, VAl, CuAl, and Oi) invariably have lower formation energies than their n-type counterparts. Particularly, VCu and CuAl have the lowest formation energies among intrinsic defects, and therefore are most likely responsible for the p-type conductivity. However, the transition levels of the VCu and CuAl defects are deep, which are responsible for the poor p-type conductivity in CuAlO2.

Defect formation of CuI-doped by group-IIB elements

2019 ◽  
Vol 33 (01) ◽  
pp. 1850423
Author(s):  
Hui Chen ◽  
Mu Gu
Keyword(s):  
First Principles ◽  
Formation Energy ◽  
Defect Formation ◽  
Valence Band Maximum ◽  
Acceptor Level ◽  
First Principles Calculations ◽  
Transition Energies ◽  
Band Maximum ◽  
P Type ◽  
Formation Energies

First-principles calculations have been performed to investigate the doping defects in CuI with group-IIB elements such as Zn, Cd and Hg. The calculated transition energies for substitutional Zn, Cd and Hg are 1.32, 1.28 and 0.60 eV, respectively. These group-IIB elements at the substitutional sites complex with a copper vacancy [Formula: see text] have the lower formation energies as compared to dopants located at the substitutional sites or interstitial sites, respectively. Among all the complex defects considered, [Formula: see text] has the lowest formation energy and it induces the acceptor level [Formula: see text] eV above the valence-band maximum (VBM), which is close to the acceptor level [Formula: see text] eV of [Formula: see text], suggesting that Hg may be a good dopant for CuI to improve its p-type conductivity.

A Model for Estimating Chemical Potentials in Ternary Semiconductor Compounds: the Case of InGaAs

MRS Advances ◽  
2017 ◽  
Vol 2 (51) ◽  
pp. 2909-2914 ◽  
Author(s):  
Vadym Kulish ◽  
Wenyan Liu ◽  
Sergei Manzhos
Keyword(s):  
Defect Formation ◽  
Chemical Potential ◽  
Doped Semiconductors ◽  
Ternary Compounds ◽  
Chemical Potentials ◽  
Semiconductor Compounds ◽  
Ternary Semiconductor ◽  
Ternary Semiconductor Compounds ◽  
Approximate Treatment ◽  
Formation Energies

ABSTRACTIn ab initio modeling of doped semiconductors, estimation of defect formation energies involving substitutional sites of ternary compounds is ambiguous due to an approximate treatment of chemical potential of the substituted atoms. We propose a model of assigning fractions of the formation energy to individual atoms of a ternary semiconductor and test it on InGaAs. The accuracy of this approximation is on the order of 0.1 eV/atom and is expected to be sufficient for many practical purposes.

Synergistic effects on band gap-narrowing in titania by doping from first-principles calculations: density functional theory studies

2011 ◽  
Vol 1352 ◽  
Author(s):  
Run Long ◽  
Niall J. English
Keyword(s):  
Visible Light ◽  
Band Gap ◽  
Density Functional ◽  
Synergistic Effects ◽  
Theoretical Calculations ◽  
Binding Energies ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Band Gap Narrowing ◽  
Formation Energies

ABSTRACTThe large intrinsic band gap in TiO2 has hindered severely its potential application for visible-light irradiation. We have used a passivated approach to modify the band edges of anatase-TiO2 by codoping of X (N, C) with transition metals (TM=W, Re, Os) to extend the absorption edge to longer visible-light wavelengths. It was found that all the codoped systems can narrow the band gap significantly; in particular, (N+W)-codoped systems could serve as remarkably better photocatalysts with both narrowing of the band gap and relatively smaller formation energies and larger binding energies than those of (C+TM) and (N+TM)-codoped systems. Our theoretical calculations help to rationalise experimental results and provide reasonably meaningful guides for experiment to develop more powerful visible-light photocatalysts.

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