scholarly journals Defect Chemistry, Sodium Diffusion and Doping Behaviour in NaFeO2 Polymorphs as Cathode Materials for Na-Ion Batteries: A Computational Study

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3243 ◽  
Author(s):  
Navaratnarajah Kuganathan ◽  
Nikolaos Kelaidis ◽  
Alexander Chroneos
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Defect Engineering ◽  
High Concentration ◽  
Functional Theory ◽  
Good Reproduction ◽  
Doping Behaviour ◽  
Engineering Strategy ◽  
Diffusion Paths ◽  
Sodium Diffusion

Minor metal-free sodium iron dioxide, NaFeO2, is a promising cathode material in sodium-ion batteries. Computational simulations based on the classical potentials were used to study the defects, sodium diffusion paths and cation doping behaviour in the α- and β-NaFeO2 polymorphs. The present simulations show good reproduction of both α- and β-NaFeO2. The most thermodynamically favourable defect is Na Frenkel, whereas the second most favourable defect is the cation antisite, in which Na and Fe exchange their positions. The migration energies suggest that there is a very small difference in intrinsic Na mobility between the two polymorphs but their migration paths are completely different. A variety of aliovalent and isovalent dopants were examined. Subvalent doping by Co and Zn on the Fe site is calculated to be energetically favourable in α- and β-NaFeO2, respectively, suggesting the interstitial Na concentration can be increased by using this defect engineering strategy. Conversely, doping by Ge on Fe in α-NaFeO2 and Si (or Ge) on Fe in β-NaFeO2 is energetically favourable to introduce a high concentration of Na vacancies that act as vehicles for the vacancy-assisted Na diffusion in NaFeO2. Electronic structure calculations by using density functional theory (DFT) reveal that favourable dopants lead to a reduction in the band gap.

scholarly journals Defect processes in F and Cl doped anatase TiO2

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Petros-Panagis Filippatos ◽  
Nikolaos Kelaidis ◽  
Maria Vasilopoulou ◽  
Dimitris Davazoglou ◽  
Nektarios N. Lathiotakis ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Photocatalytic Activity ◽  
Electron Transport ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Defect Engineering ◽  
Functional Theory ◽  
Spin Polarized ◽  
Engineering Strategy ◽  
Complete Investigation

AbstractTitanium dioxide represents one of the most widely studied transition metal oxides due to its high chemical stability, non-toxicity, abundance, electron transport capability in many classes of optoelectronic devices and excellent photocatalytic properties. Nevertheless, the wide bang gap of pristine oxide reduces its electron transport ability and photocatalytic activity. Doping with halides and other elements has been proven an efficient defect engineering strategy in order to reduce the band gap and maximize the photocatalytic activity. In the present study, we apply Density Functional Theory to investigate the influence of fluorine and chlorine doping on the electronic properties of TiO2. Furthermore, we present a complete investigation of spin polarized density functional theory of the (001) surface doped with F and Cl in order to elaborate changes in the electronic structure and compare them with the bulk TiO2.

scholarly journals Computational Study of the Electron Spectra of Vapor-Phase Indole and Four Azaindoles

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1947
Author(s):  
Delano P. Chong
Keyword(s):  
Density Functional Theory ◽  
Vapor Phase ◽  
Density Functional ◽  
Computational Study ◽  
Geometry Optimization ◽  
The Other ◽  
Functional Theory ◽  
Electron Spectra

After geometry optimization, the electron spectra of indole and four azaindoles are calculated by density functional theory. Available experimental photoemission and excitation data for indole and 7-azaindole are used to compare with the theoretical values. The results for the other azaindoles are presented as predictions to help the interpretation of experimental spectra when they become available.

scholarly journals A computational study for the reaction mechanism of metal-free cyanomethylation of aryl alkynoates with acetonitrile

RSC Advances ◽  
2021 ◽  
Vol 11 (30) ◽  
pp. 18246-18251
Author(s):  
Selçuk Eşsiz
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Computational Study ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Metal Free ◽  
Coupled Cluster Methods ◽  
High Level ◽  
Cluster Methods

A computational study of metal-free cyanomethylation and cyclization of aryl alkynoates with acetonitrile is carried out employing density functional theory and high-level coupled-cluster methods, such as [CCSD(T)].

scholarly journals Density Functional Theory and Complete Basis Set Ab Initio Computational Study of Five-, Six-, Seven- and Eight-hydrogen Coordinated Carbon Cations

1999 ◽  
Vol 23 (8) ◽  
pp. 502-503
Author(s):  
Branko S. Jursic
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Basis Set ◽  
Functional Theory ◽  
Complete Basis ◽  
Complete Basis Set ◽  
High Level

High level ab initio and density functional theory studies are performed on highly protonated methane species.

scholarly journals Application of β-Phosphorylated Nitroethenes in [3+2] Cycloaddition Reactions Involving Benzonitrile N-Oxide in the Light of a DFT Computational Study

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 26-37
Author(s):  
Karolina Zawadzińska ◽  
Karolina Kula
Keyword(s):  
Density Functional ◽  
Reaction Path ◽  
Computational Study ◽  
Cyano Group ◽  
Cycloaddition Reactions ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Reaction Channels ◽  
One Step ◽  
Step Mechanism

The regiochemistry of [3+2] cycloaddition (32CA) processes between benzonitrile N-oxide 1 and β-phosphorylated analogues of nitroethenes 2a–c has been studied using the Density Functional Theory (DFT) at the M062X/6-31+G(d) theory level. The obtained results of reactivity indices show that benzonitrile N-oxide 1 can be classified both as a moderate electrophile and moderate nucleophile, while β-phosphorylated analogues of nitroethenes 2a–c can be classified as strong electrophiles and marginal nucleophiles. Moreover, the analysis of CDFT shows that for [3+2] cycloadditions with the participation of β-phosphorylatednitroethene 2a and β-phosphorylated α-cyanonitroethene 2b, the more favored reaction path forms 4-nitro-substituted Δ2-isoxazolines 3a–b, while for a reaction with β-phosphorylated β-cyanonitroethene 2c, the more favored path forms 5-nitro-substituted Δ2-isoxazoline 4c. This is due to the presence of a cyano group in the alkene. The CDFT study correlates well with the analysis of the kinetic description of the considered reaction channels. Moreover, DFT calculations have proven the clearly polar nature of all analyzed [3+2] cycloaddition reactions according to the polar one-step mechanism.

scholarly journals Experimental and Computational Studies on N-alkylation Reaction of N-Benzoyl 5-(Aminomethyl)Tetrazole

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 704-713
Author(s):  
Younas Aouine ◽  
Aaziz Jmiai ◽  
Anouar Alami ◽  
Abdallah El Asri ◽  
Souad El Issami ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Nmr Spectroscopy ◽  
Density Functional ◽  
Computational Study ◽  
Benzyl Bromide ◽  
13C Nmr Spectroscopy ◽  
Alkylation Reaction ◽  
Computational Studies ◽  
Functional Theory ◽  
1H And 13C Nmr

The N-alkylation reaction of N-benzoyl 5-(aminomethyl)tetrazole (5-AMT) with benzyl bromide was carried out in the presence of K2CO3 as a base. Two separable regioisomers were obtained, thus their purification led to determine the proportion of each of them, and their structures were attributed essentially based on 1H and 13C NMR spectroscopy in addition to the elemental analysis and MS data. In order to confirm the results obtained at the synthesis level, a computational study was carried out by application of density functional theory (DFT) using the Becke three-parameter hybrid exchange functional and the Lee-Yang-Parr correlation functional (B3LYP).

scholarly journals A Computational Study of Direct CO2 Hydrogenation to Methanol on Pd Catalysts

2021 ◽  
Author(s):  
Igor Kowalec ◽  
Lara Kabalan ◽  
Richard Catlow ◽  
Andrew Logsdail
Keyword(s):  
Density Functional ◽  
Negative Charge ◽  
Computational Study ◽  
Adsorbed Species ◽  
Pd Catalysts ◽  
Functional Theory ◽  
Activation Barriers ◽  
Rate Determining Step ◽  
Adsorption Energies ◽  
Insight Into

<p>We investigate the mechanism of direct CO<sub>2</sub> hydrogenation to methanol on Pd (111), (100) and (110) surfaces using density functional theory (DFT), providing insight into the reactivity of CO<sub>2</sub> on Pd-based catalysts. The initial chemisorption of CO<sub>2</sub>, forming a partially charged CO<sub>2</sub><sup>δ-</sup>, is weakly endothermic on a Pd (111) surface, with an adsorption energy of 0.06 eV, and slightly exothermic on Pd (100) and (110) surfaces, with adsorption energies of -0.13 and -0.23 eV, respectively. Based on Mulliken analysis, we attribute the low stability of CO<sub>2</sub><sup>δ-</sup><sub> </sub>on the Pd (111) surface to a negative charge that accumulates on the surface Pd atoms interacting directly with the CO<sub>2</sub><sup>δ-</sup><sub> </sub>adsorbate. For the reaction of the adsorbed species on the Pd surface, HCOOH hydrogenation to H<sub>2</sub>COOH is predicted to be the rate determining step of the conversion to methanol in all cases, with activation barriers of 1.35, 1.26, and 0.92 eV on Pd (111), (100) and (110) surfaces, respectively.<br></p>

scholarly journals On local aromaticity of selected model aza-[n]circulenes (n = 6, 7, 8 and 9): Density functional theoretical study

2019 ◽  
Vol 12 (1) ◽  
pp. 70-81
Author(s):  
Denisa Cagardová ◽  
Vladimír Lukeš ◽  
Ján Matúška ◽  
Peter Poliak
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Molecular Structures ◽  
Functional Theory ◽  
Structure Of Molecules ◽  
Planar Molecules ◽  
P Type ◽  
Structural Indices ◽  
Lowest Unoccupied Molecular Orbitals ◽  
Local Aromaticity

Abstract A computational study using density functional theory is reported for selected model aza[n]circulenes (n = 6, 7, 8 and 9) and their derivatives consisting of pyrrole and benzene units. Local aromaticity of central rings was discussed and analyzed using theoretical structural indices. Depending on their molecular structures, energies of the highest occupied and lowest unoccupied molecular orbitals change from –5.23 eV to –4.08 eV and from –1.97 eV to –0.41 eV, respectively. Based on B3LYP calculated optimal geometries, electronic structure of molecules and their charge transport properties resulted in the suggestion of three planar molecules containing three or four pyrrole units as potential candidates for p-type semiconductors. Hole drift mobilities for ideal stacked dimers of these potential semiconductors were calculated and they range from 0.94 cm2·V−1·s−1 to 7.33 cm2·V−1·s−1.

scholarly journals Computational study on the mechanism of metal-free photochemical borylation of aryl halides

2021 ◽  
Author(s):  
Chenhao Tu ◽  
Nana Ma ◽  
Qingli Xu ◽  
Wenyue Guo ◽  
Lanxin Zhou ◽  
...  
Keyword(s):  
Density Functional ◽  
Uv Light ◽  
Computational Study ◽  
Halogen Bond ◽  
Bond Cleavage ◽  
Aryl Halides ◽  
Homolytic Cleavage ◽  
Functional Theory ◽  
Aryl Radicals

C-radical borylation is an significant approach for the construction of carbon−boron bond. Photochemical borylation of aryl halides successfully applied this strategy. However, precise mechanisms, such as the generation of aryl radicals and the role of base additive(TMDAM) and water, remain controversy in these reactions. In this study, photochemical borylation of aryl halides has been researched by density functional theory (DFT) calculations. Indeed, the homolytic cleavage of the C−X bond under irradiation with UV-light is a key step for generation of aryl radicals. Nevertheless, the generation of aryl radicals may also undergo the process of single electron transfer and the heterolytic carbon-halogen bond cleavage sequence, and the latter is favorable during the reaction.

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