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.

A complete ab initio thermodynamic and kinetic catalogue of the defect chemistry of hematite α-Fe2O3, its cation diffusion, and sample donor dopants

2021 ◽  
Author(s):  
Shehab Shousha ◽  
Sarah Khalil ◽  
Mostafa Youssef
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Defect Formation ◽  
Defect Chemistry ◽  
Cation Diffusion ◽  
Functional Theory ◽  
Migration Barriers ◽  
Hubbard U ◽  
And Migration ◽  
Formation Energies

This paper studies comprehensively the defect chemistry and cation diffusion in α-Fe2O3. Defect formation energies and migration barriers are calculated using density functional theory with a theoretically calibrated Hubbard U...

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.

First-principles study of the effect of lanthanum on the niobium diffusion in fcc Fe

2016 ◽  
Vol 30 (23) ◽  
pp. 1650157
Author(s):  
Xueyun Gao ◽  
Huiping Ren ◽  
Chunlong Li ◽  
Haiyan Wang ◽  
Huijie Tan
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Transformation Process ◽  
Binding Energies ◽  
Diffusion Activation Energy ◽  
Repulsive Interaction ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
And Migration

The effect of La on the diffusion of Nb in fcc Fe has been investigated using the first-principles calculations based on the density functional theory. The binding energies of Nb–vacancy, La–vacancy and La–Nb pairs have been calculated. The interactions of Nb–vacancy and La–Nb are attractive in 1nn and 2nn configurations (nn: nearest–neighbor). La atom attracts strongly with the 1nn vacancy, but has a weakly repulsive interaction with the 2nn vacancy. We consider four different Nb jumps in the presence of La atom to investigate the Nb diffusion in terms of vacancy formation and migration energy. The results suggest that La increases the diffusion activation energy of Nb in fcc Fe matrix, and is helpful to decelerate the Nb-diffusion-involved phase transformation process.

A Computational Study of Oxygen Contamination in Sb2Te3

2006 ◽  
Vol 918 ◽  
Author(s):  
John Earl Boyd ◽  
Arthur Edwards ◽  
Andrew C. Pineda
Keyword(s):  
Density Functional ◽  
Defect Formation ◽  
Computational Study ◽  
Low Concentrations ◽  
Substitutional Defects ◽  
High Concentrations ◽  
Single Oxygen Atom ◽  
Crystalline System ◽  
Single Oxygen ◽  
Formation Energies

AbstractWe present first principles electronic structure calculations of oxygen substitutional defects in the Sb2Te3 layered crystalline system and a model of amorphous Sb2Te3 using density functional theory (DFT). Our calculated formation energies for oxygen substitutional defects at Sb sites are above 2 eV, so most of our results are on the Sb2Te3-xOx [x = .0074 - .20] system, where one of two inequivalent Te sites are instead occupied by a single oxygen atom with formation energies between -1.2 eV and .2 eV. Defect formation energies for the system show a preference for oxygen atoms on the Te1 site at low concentrations that switches to the Te2 site at high concentrations at approximately 6 atomic percent. In agreement with experiment, we find that oxygen does widen the band gap, even at relatively low concentrations.

scholarly journals Ternary phase diagram of Ni-Mn-Ga: insights from ab initio calculations

2018 ◽  
Vol 185 ◽  
pp. 05012
Author(s):  
Yulia Sokolovskaya ◽  
Mikhail Zagrebin ◽  
Vasiliy Buchelnikov ◽  
Alexey Zayak
Keyword(s):  
Density Functional ◽  
Ternary Phase ◽  
Ternary Phase Diagram ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
Functional Theory ◽  
Wide Range ◽  
The Family ◽  
Compositional Variations ◽  
Formation Energies

In this work we perform a wide-range systematic study of the family off-stoichiometric Ni-Mn-Ga alloys by using the supercell approach in the framework of density functional theory. Our goal is to explore the compositional variations of the structural stability and magnetic properties of Ni-Mn-Ga compositions. As a result equilibrium lattice parameters, bulk moduli, total magnetic moments, and formation energies of a wide range of Heusler alloys have been mapped on compositional ternary diagrams.

Density functional theory study on silver clusters using dimers, trimers, and tetramers as building units

2015 ◽  
Vol 93 (3) ◽  
pp. 318-325 ◽  
Author(s):  
T.N. Rekha ◽  
Beulah J.M. Rajkumar
Keyword(s):  
Density Functional Theory ◽  
Molecular Orbital ◽  
Density Functional ◽  
Nearest Neighbor ◽  
Population Analysis ◽  
Growth Patterns ◽  
Binding Energies ◽  
Silver Clusters ◽  
Mulliken Population ◽  
Functional Theory

We systematically investigate growth patterns of small silver clusters, Agn (n ≤ 10), using density functional theory (DFT) and time-dependent density functional theory (TDDFT), considering Ag2, Ag3, and Ag4 as basic building units. Nearest-neighbor distances increase gradually with increasing n. Compared with an earlier study, where the clusters were developed by adding one atom at a time, the clusters derived in this investigation had considerably higher computed binding energies, confirming increased stability and suggesting possible growth patterns using these basic units. We used TDDFT methods to simulate the ultraviolet–visible spectra of the silver clusters, which are in good agreement with the reported experimental absorption spectrum of Ag nanoparticles. Our study indicates that the clusters formed with units of Ag3 tend to form more reactive clusters, particularly if an odd number of atoms is involved. Further, the higher level of computations employed gives better insight into the process of particle growth. The disproportionation energies of clusters built using this scheme are compared with those built one atom at a time. Mulliken population analysis of the distributions indicates the presence of polarities among the atoms in some of the cluster isomers, suggesting sites of increased activity. In addition, patterns established for the highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and HOMO–LUMO energy gaps may be used to model stable clusters with modified optoelectrical properties.

scholarly journals Ab Initio Study of MgTe Self-Interstitial (Mgi and Tei): A Wide Band Gap Semiconductor

2017 ◽  
Vol 16 ◽  
pp. 47-51
Author(s):  
Emmanuel Igumbor ◽  
Ezekiel Omotoso ◽  
Walter Ernst Meyer
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Defect Formation ◽  
Local Density ◽  
Wide Band ◽  
Shallow Donor ◽  
Generalized Gradient ◽  
Wide Band Gap ◽  
Functional Theory ◽  
Formation Energies

We present results of defect formation energies and charge state thermodynamic transition levels of Mg and Te interstitials in MgTe wurzite structure. We use the generalized gradient approximation and local density approximation functionals in the framework of density functional theory for all calculations. The formation energies of the Mg and Te interstitials in MgTe for both the tetrahedral and hexagonal configurations were obtained. The Mg and Te interstitials in MgTe depending on the functional, introduced transition state levels that are either donor or acceptor within the band gap of the MgTe. The Te interstitial exhibit charge states controlled metastability, negative-U and DX centre properties. The Mg interstitial acts as deep or shallow donor and there is no evidence of acceptor levels found for the Mg interstitial.

AN EFFICIENT CRITERION FOR THE FORMATION ENERGIES AND REACTIVITIES OF DEFECTS IN CNTs AND BNNTs

2008 ◽  
Vol 07 (04) ◽  
pp. 681-695 ◽  
Author(s):  
JUNQIAN LI ◽  
YONG CHEN ◽  
LINGANG CHEN
Keyword(s):  
Density Functional Theory ◽  
Boron Nitride ◽  
Density Functional ◽  
Boron Nitride Nanotubes ◽  
Binding Energies ◽  
Functional Theory ◽  
Defect Sites ◽  
Theoretical Predictions ◽  
Formation Energies

Directional curvature KD, was proposed as a simple and efficient criterion for the formation energies and reactivities of defects in carbon and boron nitride nanotubes. Using the periodic density functional theory, the formation energies of Stone–Wales (SW) and divacancy (DV) defects in their armchair (5,5) and zigzag (10,0) nanotubes, as well as the binding energies of the O atom adducts on these defect sites are calculated. These calculated results are found to fit well with the theoretical predictions by the directional curvature KD.

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