scholarly journals Computational mechanistic study of the unimolecular dissociation of ethyl hydroperoxide and its bimolecular reactions with atmospheric species

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Mansour H. Almatarneh ◽  
Asmaa Alnajajrah ◽  
Mohammednoor Altarawneh ◽  
Yuming Zhao ◽  
Mohammad A. Halim
Keyword(s):  
Activation Energy ◽  
Density Functional ◽  
Computational Study ◽  
Basis Sets ◽  
Mechanistic Study ◽  
Intrinsic Reaction Coordinate ◽  
Unimolecular Dissociation ◽  
Phase Reaction ◽  
Atmospheric Species ◽  
Solvation Models

Abstract A detailed computational study of the atmospheric reaction of the simplest Criegee intermediate CH2OO with methane has been performed using the density functional theory (DFT) method and high-level calculations. Solvation models were utilized to address the effect of water molecules on prominent reaction steps and their associated energies. The structures of all proposed mechanisms were optimized using B3LYP functional with several basis sets: 6-31G(d), 6-31G (2df,p), 6-311++G(3df,3pd) and at M06-2X/6-31G(d) and APFD/6-31G(d) levels of theory. Furthermore, all structures were optimized at the B3LYP/6-311++G(3df,3pd) level of theory. The intrinsic reaction coordinate (IRC) analysis was performed for characterizing the transition states on the potential energy surfaces. Fifteen different mechanistic pathways were studied for the reaction of Criegee intermediate with methane. Both thermodynamic functions (ΔH and ΔG), and activation parameters (activation energies Ea, enthalpies of activation ΔHǂ, and Gibbs energies of activation ΔGǂ) were calculated for all pathways investigated. The individual mechanisms for pathways A1, A2, B1, and B2, comprise two key steps: (i) the formation of ethyl hydroperoxide (EHP) accompanying with the hydrogen transfer from the alkanes to the terminal oxygen atom of CIs, and (ii) a following unimolecular dissociation of EHP. Pathways from C1 → H1 involve the bimolecular reaction of EHP with different atmospheric species. The photochemical reaction of methane with EHP (pathway E1) was found to be the most plausible reaction mechanism, exhibiting an overall activation energy of 7 kJ mol−1, which was estimated in vacuum at the B3LYP/6-311++G(3df,3pd) level of theory. All of the reactions were found to be strongly exothermic, expect the case of the sulfur dioxide-involved pathway that is predicted to be endothermic. The solvent effect plays an important role in the reaction of EHP with ammonia (pathway F1). Compared with the gas phase reaction, the overall activation energy for the solution phase reaction is decreased by 162 and 140 kJ mol−1 according to calculations done with the SMD and PCM solvation models, respectively.

scholarly journals Synthesis, X-Ray Crystallography, Thermal Analysis, and DFT Studies of Ni(II) Complex with 1-Vinylimidazole Ligand

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Fatih Şen ◽  
Ramazan Şahin ◽  
Muharrem Dinçer ◽  
Ömer Andaç ◽  
Murat Taş
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Basis Sets ◽  
Mulliken Charge ◽  
Monoclinic Space Group ◽  
X Ray Diffraction ◽  
Dft Methods ◽  
X Ray ◽  
X Ray Crystallography ◽  
The Density Functional Theory

The paper presents a combined experimental and computational study of hexa(1-vinylimidazole)Ni(II) perchlorate complex. The complex was prepared in the laboratory and crystallized in the monoclinic space group P21/n with a=8.442(5), b=13.686(8), c=16.041(9) Å, α=γ=90, β=96.638(5), and Z=1. The complex has been characterized structurally (by single-crystal X-Ray diffraction) and its molecular structure in the ground state has been calculated using the density functional theory (DFT) methods with 6-31G(d) and LanL2DZ basis sets. Thermal behaviour and stability of the complex were studied by TGA/DTA analyses. Besides, the nonlinear optical effects (NLO), molecular electrostatic potential (MEP), frontier molecular orbitals (FMO), and the Mulliken charge distribution were investigated theoretically.

Oxidation of Aromatic Alkynes with Nitrate Radicals (NO3•): An Experimental and Computational Study on a Synthetically Highly Versatile Radical

2007 ◽  
Vol 60 (6) ◽  
pp. 420 ◽  
Author(s):  
Uta Wille ◽  
Jilliarne Andropof
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Computational Study ◽  
Basis Sets ◽  
Wolff Rearrangement ◽  
Atom Density ◽  
Functional Studies ◽  
Vinyl Radical ◽  
Nitrate Radicals ◽  
By Products

Addition of electro- and photochemically generated nitrate radicals, NO3•, to the C≡C triple bond of aromatic alkynes 9a–9h leads to formation of 1,2-diketones 10a–10h. Surprisingly, benzophenones 11a–11h are obtained as by-products, which formally result from loss of a carbon atom. Density functional studies performed with the BHandHLYP method in combination with various basis sets revealed that 1,2-diketones result from 5-endo cyclization of the initially formed vinyl radical and loss of NO•. The key step to benzophenone formation is a γ-cleavage at the stage of the vinyl radical with release of NO2•, followed by Wolff rearrangement of the resulting α-oxo carbene.

scholarly journals Active Machine Learning for Chemical Dynamics Simulations. I. Estimating the Energy Gradient

2021 ◽  
Author(s):  
Kazuumi Fujioka ◽  
Yuheng Luo ◽  
Rui Sun
Keyword(s):  
Machine Learning ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Cost ◽  
Basis Sets ◽  
Intrinsic Reaction Coordinate ◽  
Chemical Systems ◽  
Energy Gradient ◽  
Gradient Calculation ◽  
Dynamics Simulations

Ab initio molecular dymamics (AIMD) simulation studies are a direct way to visualize chemical reactions and help elucidate non-statistical dynamics that does not follow the intrinsic reaction coordinate. However, due to the enormous amount of the ab initio energy gradient calculations needed for AIMD, it has been largely restrained to limited sampling and low level of theory (i.e., density functional theory with small basis sets). To overcome this issue, a number of machine learning (ML) methods have been employed to predict the energy gradient of the system of interest. In this manuscript, we outline the theoretical foundations of a novel ML method which trains from a varying set of atomic positions and their energy gradients, called interpolating moving ridge regression (IMRR), and directly predicts the energy gradient of a new set of atomic positions. Several key theoretical findings are presented regarding the inputs used to train IMRR and the predicted energy gradient. A hyperparameter used to guide IMRR is rigorously examined as well. The method is then applied to three bimolecular reactions studied with AIMD, including HBr+ + CO2, H2S + CH, and C4H2 + CH, to demonstrate IMRR’s performance on different chemical systems of different sizes. This manuscript also compares the computational cost of the energy gradient calculation with IMRR vs. ab initio, and the results highlight IMRR as a viable option to greatly increase the efficiency of AIMD.

Computational Study of the Decomposition of Cyclotetramethylenetetranitramine under Impact, Friction, and Electric Fields

2015 ◽  
Vol 1096 ◽  
pp. 407-412
Author(s):  
Hui Hu ◽  
Miao Miao Li ◽  
Bao Shan Wang
Keyword(s):  
Electric Fields ◽  
Energetic Materials ◽  
Density Functional ◽  
Computational Study ◽  
Minimum Energy ◽  
High Energy ◽  
High Energy Density ◽  
Basis Sets ◽  
Gas Phases ◽  
The Impact

Organic CHNO-containing high energy density materials have been widely used for storing large amounts of the chemical energies which can be rapidly transformed into heat upon various external perturbations during detonation. The sensitivity of the energetic materials is subjected to considerable concern for safety and maintenance. Periodic density functional theory with the all-electron basis sets were employed in this work to unravel the impact, friction, and electric-fields induced decomposition of HMX. The minimum energy paths for the N−NO2homolysis reactions of HMX in the bulk and gas phases were obtained. The surface-enhanced effect on the decomposition of HMX were calculated for both (010) and (100) surfaces. A general theoretical scheme has been proposed to assess the intrinsic mechanic and electrostatic sensitivities of the pure energetic materials.

scholarly journals Active Machine Learning for Chemical Dynamics Simulations. I. Estimating the Energy Gradient

2021 ◽  
Author(s):  
Kazuumi Fujioka ◽  
Rui Sun
Keyword(s):  
Machine Learning ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Cost ◽  
Basis Sets ◽  
Intrinsic Reaction Coordinate ◽  
Chemical Systems ◽  
Energy Gradient ◽  
Gradient Calculation ◽  
Dynamics Simulations

Ab initio molecular dymamics (AIMD) simulation studies are a direct way to visualize chemical reactions and help elucidate non-statistical dynamics that does not follow the intrinsic reaction coordinate. However, due to the enormous amount of the ab initio energy gradient calculations needed for AIMD, it has been largely restrained to limited sampling and low level of theory (i.e., density functional theory with small basis sets). To overcome this issue, a number of machine learning (ML) methods have been employed to predict the energy gradient of the system of interest. In this manuscript, we outline the theoretical foundations of a novel ML method which trains from a varying set of atomic positions and their energy gradients, called interpolating moving ridge regression (IMRR), and directly predicts the energy gradient of a new set of atomic positions. Several key theoretical findings are presented regarding the inputs used to train IMRR and the predicted energy gradient. A hyperparameter used to guide IMRR is rigorously examined as well. The method is then applied to three bimolecular reactions studied with AIMD, including HBr+ + CO2, H2S + CH, and C4H2 + CH, to demonstrate IMRR’s performance on different chemical systems of different sizes. This manuscript also compares the computational cost of the energy gradient calculation with IMRR vs. ab initio, and the results highlight IMRR as a viable option to greatly increase the efficiency of AIMD.

Corrigendum to: Oxidation of Aromatic Alkynes with Nitrate Radicals (NO3•): An Experimental and Computational Study on a Synthetically Highly Versatile Radical

2007 ◽  
Vol 60 (7) ◽  
pp. 547 ◽  
Author(s):  
Uta Wille ◽  
Jilliarne Andropof
Keyword(s):  
Triple Bond ◽  
Density Functional ◽  
Computational Study ◽  
Basis Sets ◽  
Wolff Rearrangement ◽  
Atom Density ◽  
Functional Studies ◽  
Vinyl Radical ◽  
Nitrate Radicals ◽  
By Products

Addition of electro- and photochemically generated nitrate radicals, NO3•, to the C≡C triple bond of aromatic alkynes 9a–9h leads to formation of 1,2-diketones 10a–10h. Surprisingly, benzophenones 11a–11h are obtained as by-products, which formally result from loss of a carbon atom. Density functional studies performed with the BHandHLYP method in combination with various basis sets revealed that 1,2-diketones result from 5-endo cyclization of the initially formed vinyl radical and loss of NO•. The key step to benzophenone formation is a γ-cleavage at the stage of the vinyl radical with release of NO2•, followed by Wolff rearrangement of the resulting α-oxo carbene.

scholarly journals Amino acetaldehyde conformers: structure and spectroscopic properties

2019 ◽  
Vol 492 (2) ◽  
pp. 1827-1833
Author(s):  
Pilar Redondo ◽  
Miguel Sanz-Novo ◽  
Antonio Largo ◽  
Carmen Barrientos
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Spectroscopic Properties ◽  
Phase Reaction ◽  
Functional Theory ◽  
Singlet Potential Energy Surface ◽  
Infrared Intensities ◽  
Anharmonic Corrections ◽  
Candidate Molecule

ABSTRACT We present a computational study of the different conformers of amino acetaldehyde. This molecule is a precursor of glycine and also an isomer of the detected molecules acetaldehyde and methylformamide. In addition, a previous theoretical result shows that amino acetaldehyde could be formed from the gas phase reaction of formamide with CH$_{5}^{+}$. Different computational approaches, going from density functional theory (DFT) to coupled cluster (CC) calculations, are employed for the characterization of the amino acetaldehyde conformers. We locate four low-lying conformation on the singlet potential energy surface (PES), two with a synperiplanar arrangement of the carboxylic oxygen atom and the NH2 group, and the other two conformers with an anticlinal disposition. All levels of theory predict the conformer with a synperiplanar arrangement and the H atoms of the NH2 group pointing in the direction of the oxygen, denoted as in-sp-amino acetaldehyde, as the most stable. The viability of the interconversion processes between the four conformers in space is analysed. Relevant spectroscopic parameters to rotational spectroscopy with ‘spectroscopic’ accuracy at the composite level are reported. Vibrational frequencies and infrared intensities are also computed at the CC with single and double excitations (CCSD) level including anharmonic corrections. This information could help in the experimental characterization of amino acetaldehyde that could be considered as a good candidate molecule to be searched for in space.

New Chalcone Derivative: Synthesis, Characterization, Computational Studies and Antioxidant Activity

2019 ◽  
Vol 17 (1) ◽  
pp. 46-53
Author(s):  
Reşat Ustabaş ◽  
Nevin Süleymanoğlu ◽  
Namık Özdemir ◽  
Nuran Kahriman ◽  
Ersan Bektaş ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Density Functional ◽  
Computational Study ◽  
Dft Method ◽  
Basis Set ◽  
Basis Sets ◽  
Isomeric Form ◽  
Compound I ◽  
Chalcone Derivative ◽  
Reducing Ability

A new chalcone derivative, called as 1-(4-(benzylideneamino)phenyl)-3-(furan-2-yl)prop-2- en-1-one (I), was synthezised and characterized by spectral methods (infrared (IR) and proton and carbon- 13 nuclear magnetic resonance (1H- and 13C-NMR) spectroscopy). A computational study was performed by the density functional theory (DFT) method. Spectral data of compound I optimized by using 6-311G(d,p) and 6-311++G(d,p) basis sets were obtained by 6-311++G(d,p) basis set. The E-Z isomerism for newly synthesized chalcone derivative was investigated by considering four isomeric form, E/E, E/Z, Z/E and Z/Z. The results show that, as assumed and thus named, the chalcone derivative is in the E/E form. In addition, quantum chemical parameters were calculated by using DFT method with 6-311++G(d,p) basis set. Antioxidant activity of compound I was determined by the ferric reducing ability of plasma (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay methods. Compound I has low antioxidant activity.

scholarly journals Computational Study of D-glucose and its Differential Cognitive Effects on Well-being and Quality of Life

2020 ◽  
Vol 4 (3) ◽  
pp. 27-37
Author(s):  
Sohail Nadeem ◽  
Ayesha Mohyuddin ◽  
Mohsin Javed ◽  
Abdul Hafeez ◽  
Tayyaba Jamil ◽  
...  
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Well Being ◽  
Basis Sets ◽  
Functional Theory ◽  
Nmr Spectrum ◽  
Basic Set ◽  
The Density Functional Theory ◽  
Ir And Raman

GAMESS computational chemistry package is a freeware available on the web. It has been successfully applied for the structure elucidation of the commonly available D-glucose. In the current research, IR and Raman spectra of D-glucose were theoretically calculated by utilizing the density functional theory (DFT), combined with B3LYP/3-21G basic set. IR and Raman activities were estimated through the GAMESS computational package. Moreover, the NMR spectrum was also obtained through the Gaussian 09 package. Theoretically calculated and experimentally calculated results were compared using the B3LYP/3-21G level of theory. The results of both calculations were nearly the same. The optimization of structure with the various levels of theory and Basis sets was studied and the best results were obtained using B3LYP/3-21G, and these results agreed considerably with the experimental results. The current computational analysis may be useful to predict complex carbohydrate precursors and other carbohydrate molecules.

Theoretical Investigation of H2 Interactions on ZnO Cluster: DFT Approach

2018 ◽  
Vol 17 (03) ◽  
pp. 1760041 ◽  
Author(s):  
A. Aruna Devi ◽  
S. Vidya ◽  
P. K. Rai ◽  
B. G. Jeyaprakash
Keyword(s):  
Binding Energy ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Energy Gap ◽  
Computational Study ◽  
Mulliken Charge ◽  
Intrinsic Reaction Coordinate ◽  
Adsorption Sites ◽  
Dissociation Mechanisms ◽  
Adsorption And Dissociation

A computational study on adsorption and dissociation mechanisms of H2 molecule on ZnO cluster was analysed using Density Functional Theory (DFT) approach in Gaussian 09 software. The stable sites for hydrogen adsorption were inferred from the adsorption energy and bond length. Further investigations such as Mulliken charge, HOMO–LUMO energy gap and intrinsic reaction coordinate (IRC) were performed for the stable adsorption sites. It infers that the (ZnO)6 cluster has the highest binding energy of 1.851[Formula: see text]eV (O-site) and the least binding energy of [Formula: see text]3.865[Formula: see text]eV (O-site), showing most favorable size for both adsorption and dissociation of H2 molecule. The IRC plot clearly shows the dissociation mechanism of hydrogen on the ZnO cluster.

Sign in / Sign up

Export Citation Format

Share Document