Benchmark approach to search of cost‐effective and accurate density functional for homolytic cleavage of C─Mg bond of Grignard reagent

2019 ◽  
Vol 120 (4) ◽  
Author(s):  
Naveen Kosar ◽  
Khurshid Ayub ◽  
Mazhar A. Gilani ◽  
Faheem Shah ◽  
Tariq Mahmood
Keyword(s):  
Grignard Reagent ◽  
Density Functional ◽  
Cost Effective ◽  
Homolytic Cleavage ◽  
Benchmark Approach

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.

scholarly journals Electronic structure and core electron fingerprints of caesium-based multi-alkali antimonides for ultra-bright electron sources

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Caterina Cocchi ◽  
Sonal Mistry ◽  
Martin Schmeißer ◽  
Raymond Amador ◽  
Julius Kühn ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Cost Effective ◽  
Binding Energies ◽  
Many Body ◽  
Core Electron ◽  
Operational Conditions ◽  
Electron Sources ◽  
Level Shifts ◽  
Many Body Perturbation Theory

AbstractThe development of novel photocathode materials for ultra-bright electron sources demands efficient and cost-effective strategies that provide insight and understanding of the intrinsic material properties given the constraints of growth and operational conditions. To address this question, we propose a viable way to establish correlations between calculated and measured data on core electronic states of Cs-K-Sb materials. To do so, we combine first-principles calculations based on all-electron density-functional theory on the three alkali antimonides Cs3Sb, Cs2KSb, and CsK2Sb with x-ray photoemission spectroscopy (XPS) on Cs-K-Sb photocathode samples. Within the GW approximation of many-body perturbation theory, we obtain quantitative predictions of the band gaps of these materials, which range from 0.57 eV in Cs2KSb to 1.62 eV in CsK2Sb and manifest direct or indirect character depending on the relative potassium content. Our theoretical electronic-structure analysis also reveals that the core states of these systems have binding energies that depend only on the atomic species and their crystallographic sites, with largest shifts of the order of 2 eV and 0.5 eV associated to K 2p and Sb 3d states, respectively. This information can be correlated to the maxima in the XPS survey spectra, where such peaks are clearly visible. In this way, core-level shifts can be used as fingerprints to identify specific compositions of Cs-K-Sb materials and their relation with the measured values of quantum efficiency. Our results represent the first step towards establishing a robust connection between the experimental preparation and characterization of photocathodes, the ab initio prediction of their electronic structure, and the modeling of emission and beam formation processes.

scholarly journals Metal-induced n+/n homojunction for ultrahigh electron mobility transistors

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Ji-Min Park ◽  
Hyoung-Do Kim ◽  
Hongrae Joh ◽  
Seong Cheol Jang ◽  
Kyung Park ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Field Effect ◽  
Density Functional ◽  
Metal Layer ◽  
Cost Effective ◽  
Interface Layer ◽  
Field Effect Mobility ◽  
High Concentration ◽  
Large Area ◽  
Electron Mobility Transistors

AbstractA self-organized n+/n homojunction is proposed to achieve ultrahigh performance of thin film transistors (TFTs) based on an amorphous (Zn,Ba)SnO3 (ZBTO) semiconductor with sufficiently limited scattering centers. A deposited Al layer can induce a highly O-deficient (n+) interface layer in the back channel of a-ZBTO without damaging the front channel layer via the formation of a metal-oxide interlayer between the metal and back channel. The n+ layer can significantly improve the field-effect mobility by providing a relatively high concentration of free electrons in the front n-channel ZBTO, where the scattering of carriers is already controlled. In comparison with a Ti layer, the Al metal layer is superior, as confirmed by first-principles density functional theory (DFT) calculations, due to the stronger metal-O bonds, which make it easier to form a metal oxide AlOx interlayer through the removal of oxygen from ZBTO. The field-effect mobility of a-ZBTO with an Al capping layer can reach 153.4 cm2/Vs, which is higher than that of the pristine device, i.e., 20.8 cm2/Vs. This result paves the way for the realization of a cost-effective method for implementing indium-free ZBTO devices in various applications, such as flat panel displays and large-area electronic circuits.

Cost-effective promoter-doped Cu-based bimetallic catalysts for the selective hydrogenation of C2H2 to C2H4: the effect of the promoter on selectivity and activity

2018 ◽  
Vol 20 (25) ◽  
pp. 17487-17496 ◽  
Author(s):  
Riguang Zhang ◽  
Bo Zhao ◽  
Leilei He ◽  
Anjie Wang ◽  
Baojun Wang
Keyword(s):  
Density Functional Theory ◽  
Selective Hydrogenation ◽  
Bimetallic Catalysts ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Cost Effective ◽  
Microkinetic Modeling ◽  
Functional Theory ◽  
Cu Catalysts

Different metal promoter M-modified Cu catalysts have been employed to fully investigate the selective hydrogenation of C2H2 using density functional theory calculations together with microkinetic modeling.

scholarly journals SVECV-F12: A Composite Scheme for an Accurate and Cost Effective Evaluation of Reaction Barriers. I. Benchmarking Using the HTBH38/08 and NHTBH38/08 Barrier Heights Databases

2020 ◽  
Author(s):  
Oscar Ventura
Keyword(s):  
Density Functional ◽  
Cost Effective ◽  
Basis Set ◽  
Barrier Heights ◽  
Composite Methods ◽  
Complete Basis Set ◽  
Complete Basis Set Limit ◽  
Complete Set ◽  
Reaction Barriers ◽  
Better Than

A simple version of a composite scheme is described, based on a combination of density functional geometry and frequencies evaluation, valence energies obtained using the CCSD(T)-f12 method extrapolated to the complete basis set limit, and core-valence correlation corrections employing the MP2 method. The procedure was applied to the 38 reactions in Truhlar’s HTBH38/08 and NHTBH38/08 databases. Mean unsigned deviation (MUD) for the complete set of 68 independent barriers is 0.43 kcal mol-1, compared to 1.37 kcal/mol for G4 and 1.69 kcal/mol for the dispersioncorrected M06-2X method. Its accuracy is also better that that of other calculations using composite methods of similar cost. The MUD of the new scheme on the barriers in the DBH24/08 subset (12 out of the 38 reactions in both other sets) is 0.31 kcal mol-1, better than that obtained at the expensive CCSD(T,full)/aug-cc-pCV(T+d)Z level (0.46 kcal mol-1) and comparable to the most exact (and costly) Wn calculations (MUD=0.14 kcal mol-1). The maximum unsigned deviation (MaxUD) of the new method for all the reactions studied is 1.71 kcal/mol. G4 and M06-2X, on the other side, exhibit MaxUDs of 6.7 and 8.4 kcal/mol respectively

Understanding the Excited State Photophysics of Pyrrolopyrrole-Dione Isomers and Derivatives Using Time-Dependence Density Functional Theory

2017 ◽  
Vol 05 (03) ◽  
pp. 1750009
Author(s):  
Teck Lip Dexter Tam ◽  
Ting Ting Lin ◽  
Steven Lukman
Keyword(s):  
Density Functional Theory ◽  
Photodynamic Therapy ◽  
Excited State ◽  
Time Dependence ◽  
Density Functional ◽  
Photophysical Properties ◽  
Cost Effective ◽  
Time Dependent ◽  
Functional Theory ◽  
Dependent Density

The ability to understand and predict excited state photophysics is vital for the development of photo- and electroluminescence materials, as well as light harvesting materials and photodynamic therapy. Herein, we demonstrate that single determinant time-dependent density functional theory can be computationally cost-effective and has the ability to explain both experimental singlet and triplet dynamics of pyrrolo[3,4-[Formula: see text]]pyrrole-1,4-dione and pyrrolo[3,2-b]pyrrole-2,5-dione isomers with intriguing photophysical properties. We also used the methodology to predict the photophysical properties of pyrrolo[3,4-c]pyrrole-1,3-dione and a hypothetical hybrid pyrrolo[3,4-b]pyrrole-2,4-dione isomers.

scholarly journals Electrochemically Desulfurized Molybdenum Disulfide (MoS2) and Reduced Graphene Oxide Aerogel Composites as Efficient Electrocatalysts for Hydrogen Evolution

2020 ◽  
Vol 20 (10) ◽  
pp. 6191-6214 ◽  
Author(s):  
Sanju Gupta ◽  
Taylor Robinson ◽  
Nicholas Dimakis
Keyword(s):  
Hydrogen Production ◽  
Molybdenum Disulfide ◽  
Density Functional ◽  
Three Dimensional ◽  
Cost Effective ◽  
Clean Energy ◽  
Nanoporous Structure ◽  
Energy Technologies ◽  
Recent Developments ◽  
Hybrid Aerogels

Recent developments in graphene related materials including molybdenum disulfide (MoS2) is gaining popularity as efficient and cost-effective nanoscale electrocatalyst essential for hydrogen production. These “clean” energy technologies require delicate control over geometric, morphological, chemical and electronic structure affecting physical and electrochemical catalytic properties. In this work, we prepared three-dimensional hierarchical mesoporous aerogels consisting of two-dimensional functionalized graphene and MoS2 nanosheets of varying ratio of components under hydrothermal–solvothermal conditions (P <20 bar, T <200 °C). We systematically characterized these hybrid aerogels in terms of surface morphology, microstructure, understand heterointerfaces interaction through electron microscopy, X-ray diffraction, optical absorption and emission and Raman spectroscopy, besides electrochemical properties prior to and post electrochemical desulfurization that induces finely controlled sulfur vacancies. They feature enhanced electrical conductivity by means of eliminating contact resistance and meso-/nanoporous structure facilitating faster ion diffusion (mass transport). We demonstrate that controlled defects density, edges plane sites (nanowalls), mesoscale porosity and topological interconnectedness (monolithic aerogel sheets) invoked can accelerate electrocatalytic hydrogen production. For instance, low over potential with Tafel slope ~77 mV·dec-1 for 60 wt.% MoS2, highcurrent density, and good stability was achieved with desulfurization. These results are compared with continuous multilayer MoS2 films highlighting the multiple role of tunable structure and electronic properties. The adjacent S-vacancy defectsinduced increase in density of states, dissociation and confinement of water molecules at the pore edge and planar S-vacancy sites calculated using density functional theory helped in establishing improved heterogeneous electrocatalytic rate. This is supported with combined measurements of diffusion coefficient and heterogeneous electron transfer rate via surface-sensitive scanning electrochemical microscopy (SECM) technique.

One-Step Synthesis of Methoxylated Phloroglucinol Derivatives Promoted by Niobium Pentachloride: An Experimental and Theoretical Approach

Synthesis ◽  
2017 ◽  
Vol 49 (11) ◽  
pp. 2402-2410 ◽  
Author(s):  
Willian dos Santos ◽  
Eliezer de Oliveira ◽  
Francisco Lavarda ◽  
Ives Leonarczyk ◽  
Marco Ferreira ◽  
...  
Keyword(s):  
Multicomponent Reaction ◽  
Density Functional ◽  
Reaction Times ◽  
Cost Effective ◽  
Reactive Intermediates ◽  
Important Class ◽  
Functional Theory ◽  
Niobium Pentachloride ◽  
Phloroglucinol Derivatives ◽  
One Step

Phloroglucinol derivatives are an important class of natural compounds featuring the rhodomyrtone derivatives. In this work, the synthesis of compounds with a structure core of rhodomyrtosone I is described using a multicomponent reaction between aldehyde derivatives, dihydroresorcinol, and 3,5-dimethoxyphenol promoted by niobium pentachloride. This new method is simple, cost-effective, and provides a good yield. In addition, it can be conducted in good reaction times. Using Density Functional Theory (DFT) studies, bases are provided for a proposed reaction mechanism for the multicomponent reaction by exploring the energetics of proposed reactive intermediates and transition states.

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