Defect Properties in GaN: Ab Initio and Empirical Potential Calculations

2005 ◽  
Vol 475-479 ◽  
pp. 3087-3090 ◽  
Author(s):  
Fei Gao ◽  
Eric J. Bylaska ◽  
William J. Weber
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Reasonable Agreement ◽  
Stable Configuration ◽  
Functional Theory ◽  
Empirical Potential ◽  
Antisite Defects ◽  
Formation Energies ◽  
Dynamics Method ◽  
Weber Potential

The defect properties and atomic configurations in GaN have been comparatively investigated using density functional theory (DFT) and molecular dynamics method with two representative potentials. The DFT calculations show that the relaxation of vacancies is generally small, but the relaxation around antisite defects is large. The N interstitials, starting from any possible configurations, eventually relax into a N+-N< 0 2 11 > split interstitial. In the case of Ga interstitials, the most stable configuration is a Ga octahedral interstitial, but the Ga+-Ga< 0 2 11 > split interstitial can bridge the gap between non-bounded Ga atoms. The formation energies of vacancies and antisite defects obtained using the Stillinger-Weber potential (SW) are in reasonable agreement with those obtained by DFT calculations, whereas the Tersoff-Brenner (TB) potential better describes the behavior of N interstitials.

scholarly journals Electron Self-trapping in Ge2 Se3 and its Role in Ag and Sn Incorporation

2012 ◽  
Vol 1431 ◽  
Author(s):  
Arthur H. Edwards ◽  
Kristy A. Campell ◽  
Andrew C. Pineda
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Dft Calculations ◽  
Fermi Level ◽  
Density Functional ◽  
Functional Theory ◽  
Periodic Model ◽  
Self Trapping ◽  
Formation Energies

ABSTRACTWe present a set of density functional theory (DFT) calculations on the electronic structure of Ag and Sn in Ge2 Se3 in a periodic model. We show that electron self-trapping is a persistent feature in the presence of many defects. Ag and Sn autoionize upon entering Ge2 Se3 becoming Ag+ and Sn2+ , respectively, and the freed electrons self trap at the lowest energy site. Both Ag and Sn can substitute for Ge, and we present formation energies as a function of Fermi level that show that Sn can substantially alter the incorporation of Ag into the Ge2Se3 network.

X-Ray structures, Mössbauer hyperfine parameters, and molecular orbital descriptions of the phthalocyaninato iron(II) azole complexes

2020 ◽  
Vol 24 (05n07) ◽  
pp. 894-903
Author(s):  
Dustin E. Nevonen ◽  
Laura S. Ferch ◽  
Victor Y. Chernii ◽  
David E. Herbert ◽  
Johan van Lierop ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Dft Calculations ◽  
Electronic Structures ◽  
Density Functional ◽  
Reasonable Agreement ◽  
Hyperfine Parameters ◽  
Functional Theory ◽  
X Ray ◽  
X Ray Crystallography

The electronic structures of a set of PcFe(azole)2 complexes (azole = imidazole, [Formula: see text]-methylimidazole, pyrazole, isoxazole, thiazole, 1,2,4-triazole, 3-amino-1,2,4,-triazole, and 5-amino-1,2,3,4-tetrazole) were examined by Mössbauer spectroscopy and Density Functional Theory (DFT) calculations. In addition, the geometric distortions in these compounds were elucidated by X-ray crystallography for imidazole, pyrazole, and thiazole-containing compounds. Predicted by DFT calculations, Mössbauer hyperfine parameters for all compounds are in reasonable agreement with experimental results, and the influence of the [Formula: see text]-donor and [Formula: see text]-acceptor properties of the axial azoles on the electronic structure of the PcFe(azole)2 complexes is demonstrated by comparison with the reference PcFePy2 compound.

scholarly journals The Vacancy Energy in Metals: Cu, Ag, Ni, Pt, Au, Pd, Ir and Rh

2019 ◽  
pp. 1-12
Author(s):  
T. H. Akande ◽  
F. Matthew-Ojelabi ◽  
G. S. Agunbiade ◽  
E. B. Faweya ◽  
A. O. Adeboje
Keyword(s):  
Density Functional ◽  
Reasonable Agreement ◽  
Vacancy Formation ◽  
Embedded Atom Method ◽  
Heat Of Solution ◽  
Functional Theory ◽  
Surface Energies ◽  
Embedded Atom ◽  
Experimental Values ◽  
Formation Energies

The predictive calculations of vacancy formation energies in metals: Cu, Ag, Ni, Pt, Au, Pd, Ir and Rh are presented. The energy is given as a function of electron density. Density functional theory underestimates the vacancy formation energy when structural relaxation is included. The unrelaxed mono-vacancy formation, unrelaxed di-vacancy formation, unrelaxed di-vacancy binding and low index surface energies of the fcc transition metals Cu, Ag, Ni, Pt, Au, Pd, Ir and Rh has been calculated using embedded atom method. The values for the vacancy formation energies agree with the experimental value. We also calculate the elastic constants of the metals and the heat of solution for the binary alloys of the selected metals. The average surface energies calculated by including the crystal angle between planes (hkl) and (111) correspond to the experiment for Cu, Ag, Ni, Pt and Pd. The calculated mono-vacancy formation energies are in reasonable agreement with available experimental values for Cu, Ag, Au and Rh. The values are higher for Pt and Ir while smaller values were recorded for Ni and Pd. The unrelaxed di-vacancy binding energy calculated agrees with available experimental values in the case of Cu, Ni, Pt and Au. 

scholarly journals Density-Functional Theory Study of Hydrogen Induced Platelets in Silicon

2011 ◽  
Vol 1370 ◽  
Author(s):  
Liviu Bîlteanu ◽  
Jean-Paul Crocombette
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Stable Configuration ◽  
Density Functional Theory Study ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Hydrogen Molecules ◽  
The One ◽  
Infinite Planar

ABSTRACTIn this contribution we present the results of Density-Functional Theory (DFT) calculations of platelets as modelled by infinite planar arrangements of hydrogen atoms and vacancies in (100) planes of silicon. From the observation of the relaxed platelet structures and the comparison of their energy with the one of hydrogen molecules dissolved in silicon we were able to evidence several features. A planar arrangement of hydrogen atoms inserted in the middle of Si-Si bonds proves unstable and Si bonds must be broken for the platelet to be stable. In the (100) plane the most stable configuration is the one with two Si-H bonds (a so-called SiH2 structure). It is possible to generate SiH3 structures which are more stable than hydrogen dissolved in Si bulk but less than SiH2 structures but SiH1 or SiH4 sometimes observed in experiments prove unstable.

Density Functional Theory and Ab Initio Molecular Dynamics Study of the Effect of Ti and Zr Transition Metals in D03 Fe3Al

2012 ◽  
Vol 706-709 ◽  
pp. 1095-1099
Author(s):  
Sara Chentouf ◽  
Jean Marc Raulot ◽  
Hafid Aourag ◽  
Thierry Grosdidier
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Dft Calculations ◽  
Ab Initio ◽  
Density Functional ◽  
Md Simulations ◽  
Functional Theory ◽  
Ab Initio Md ◽  
Increasing Temperature ◽  
Formation Energies

The formation energies of the T.M impurities Ti and Zr were calculated using DFT calculations at absolute zero and ab initio MD simulations at 300 K. We found that, with increasing temperature, Zr impurities become more stable and prefer to segregate at the interface of ∑5 (310)[001] grain boundary. In the case of Ti, the results show that it remains a stable defect when temperature increases.

scholarly journals Formation, Stability and Magnetism of New Gd3TAl3Ge2 Quaternary Compounds (T = Mn, Cu)

2019 ◽  
Vol 289 ◽  
pp. 93-101
Author(s):  
Manish K. Kashyap ◽  
Timothy A. Hackett ◽  
Alessia Provino ◽  
Arjun K. Pathak ◽  
Vitalij K. Pecharsky ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Experimental Investigations ◽  
Stable Phase ◽  
Functional Theory ◽  
Quaternary Compounds ◽  
General Chemical ◽  
Existence And Stability ◽  
The Stability ◽  
Formation Energies

A study on the formation and stability of new quaternary compounds with the general chemical formula Gd3TAl3Ge2(T = Mn, Cu) has been undertaken by experimental investigations (SEM-EDX, DTA and XRD) and density functional theory (DFT) calculations. These compounds crystallize in the hexagonal Y3NiAl3Ge2-type structure (hP9, P–62m, Z = 1) (an ordered, quaternary derivative of the ternary ZrNiAl or of the binary Fe2P prototypes), with lattice parameters values a = 7.0239(2) Å and c = 4.2580(1) Å for Gd3MnAl3Ge2and a = 7.0434(1) Å and c = 4.2089(1) Å for Gd3CuAl3Ge2. DTA suggests a peritectic reaction for the formation of these compounds (at 1245°C for Gd3CuAl3Ge2). The existence and stability of these phases has been explained on the basis of DFT calculations, and a comparison of ground state properties of the studied compounds with the earlier known Gd3CoAl3Ge2phase is outlined. The negative formation energies in all three cases govern the stability of compounds from theory as well, predicting Gd3MnAl3Ge2as the most stable phase with highest formation energy (–13.01 eV/f.u.). The total DOS are generic in nature and suggest the robust magnetism, with the Gd-f moments of ≈7 μB. An antiparallel coupling among Gd-f and T-d states is observed for all compounds, as usually seen in rare earth (R) - transition metal (T) compounds. Preliminary magnetization measurements on Gd3MnAl3Ge2show two ferromagnetic/ferrimagnetic (FM/FIM) like transitions at TC1= 142 K and TC2= 97 K, with another anomaly seen at ≈15 K. Isothermal magnetization data show no hysteresis even at 5 K, and the magnetization does not saturate up to 50 kOe, further suggesting a possible FIM behavior.

scholarly journals First Principles Calculations and Experiments to Determine the Hydrogenation Process of Cu-Li-Mg

2012 ◽  
Vol 730-732 ◽  
pp. 799-804
Author(s):  
Maria Helena Braga ◽  
Maria Helena Sá ◽  
Jorge A. Ferreira ◽  
Luke L. Daemen
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
First Principles ◽  
Periodic Table ◽  
Density Functional ◽  
Nearest Neighbors ◽  
Stable Configuration ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Cubic Structure

Density Functional Theory (DFT) calculations were performed. They were firstly implemented to optimize the structure and refine the stoichiometry of the only ternary compound, CuLi0.08Mg1.92 of the Cu-Li-Mg system. Furthermore using DFT, several possible structures of CuMg2Hx were optimized. Since most of the hydrides are cubic structures or can be considered as distortions of a cubic structure, we have started calculations for CuMg2Hx (x = 4 - 6)with tetragonal and monoclinic structures, similar to those of the hydrides formed by the nearest neighbors of Cu and Mg in the periodic table: NiMg2H4 and CoMg2H5 (e.g. monoclinic C2/c and tetragonal P4/nmm, respectively). It can be concluded that the most stable configuration corresponds to CuMg2H5 with C2/c structure. We have performed several neutron scattering experiments that are in agreement with the first principles calculations.

γ-Valerolactone-Introduced Controlled-Isomerization of Glucose for Lactic Acid Production over Sn-Beta Catalyst

2021 ◽  
Author(s):  
Xinpeng Zhao ◽  
Zhimin Zhou ◽  
hu luo ◽  
Yanfei Zhang ◽  
Wang Liu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Lactic Acid ◽  
Dft Calculations ◽  
Acid Production ◽  
Density Functional ◽  
Lactic Acid Production ◽  
Hydrothermal Conversion ◽  
Functional Theory ◽  
Environment Friendly

Combined experiments and density functional theory (DFT) calculations provided insights into the role of the environment-friendly γ-valerolactone (GVL) as a solvent in the hydrothermal conversion of glucose into lactic acid...

Mechanistic understanding of the Cu(i)-catalyzed domino reaction constructing 1-aryl-1,2,3-triazole from electron-rich aryl bromide, alkyne, and sodium azide: a DFT study

2021 ◽  
Author(s):  
Hanlin Gan ◽  
Liang Peng ◽  
Feng Long Gu
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Sodium Azide ◽  
Density Functional ◽  
Dft Study ◽  
Domino Reaction ◽  
Aryl Bromide ◽  
Functional Theory ◽  
Mechanistic Understanding

The mechanism of the Cu(i)-catalyzed domino reaction furnishing 1-aryl-1,2,3-triazole assisted by CuI and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is explored with density functional theory (DFT) calculations.

Graph theory-based reaction pathway searches and DFT calculations for the mechanism studies of free radical-initiated peptide sequencing mass spectrometry (FRIPS MS): a model gas-phase reaction of GGR tri-peptide

2020 ◽  
Vol 22 (9) ◽  
pp. 5057-5069 ◽  
Author(s):  
Jae-ung Lee ◽  
Yeonjoon Kim ◽  
Woo Youn Kim ◽  
Han Bin Oh
Keyword(s):  
Graph Theory ◽  
Dft Calculations ◽  
Gas Phase ◽  
Density Functional ◽  
Reaction Pathway ◽  
Peptide Sequencing ◽  
Phase Reaction ◽  
Functional Theory ◽  
Fragmentation Mechanisms ◽  
Gas Phase Fragmentation

A new approach for elucidating gas-phase fragmentation mechanisms is proposed: graph theory-based reaction pathway searches (ACE-Reaction program) and density functional theory (DFT) calculations.

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