Quantum chemical study of inner-sphere complexes of trivalent lanthanide and actinide ions on the corundum (110) surface

2013 ◽  
Vol 101 (9) ◽  
pp. 561-570
Author(s):  
R. Polly ◽  
B. Schimmelpfennig ◽  
M. Flörsheimer ◽  
Th. Rabung ◽  
T. Kupcik ◽  
...  
Keyword(s):  
Metal Ions ◽  
Density Functional ◽  
Single Point ◽  
Quantum Chemical Study ◽  
Basis Sets ◽  
Water Molecules ◽  
Point Energy ◽  
Inner Sphere ◽  
Sphere Complex ◽  
Inner Sphere Complexes

Summary Sorption plays a major role in the safety assessment of nuclear waste disposal. In the present theoretical study we focused on understanding the interaction of trivalent lanthanides and actinides (La3+, Eu3+ and Cm3+) with the corundum (110) surface. Optimization of the structures were carried out using density functional theory with different basis sets. Additionally, Møller-Plesset perturbation theory of second order was used for single point energy calculations. We studied the structure of different inner-sphere complexes depending on the surface deprotonation and the number of water molecules in the first coordination shell. The most likely structure of the inner-sphere complex (tri- or tetradentate) was predicted. For the calculations we used a cluster model for the surface. By deprotonating the cluster a chemical environment at elevated pH values was mimicked. Our calculations predict the highest stability for a tetradentate inner-sphere surface complexes with five water molecules remaining in the first coordination sphere of the metal ions. The formation of the inner-sphere complexes is favored when a coordination takes place with at most one deprotonated surface aluminol group located beneath the inner-sphere complex. The mutual interaction between sorbing metal ions at the surface is studied as well. The minimal possible distance between two inner-sphere sorbed metal ions at the surface was determined to be 530 pm.

scholarly journals Computational Study of the Dissociation Reactions of Secondary Ozonide

Atmosphere ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 100 ◽  
Author(s):  
Mansour H. Almatarneh ◽  
Shefa’ F. Alrebei ◽  
Mohammednoor Altarawneh ◽  
Yuming Zhao ◽  
Abd Al-Aziz Abu-Saleh
Keyword(s):  
Barrier Height ◽  
Computational Study ◽  
Reaction Pathway ◽  
Single Point ◽  
Water Dimer ◽  
Basis Set ◽  
Basis Sets ◽  
Water Molecules ◽  
Point Energy ◽  
Secondary Ozonide

This contribution presents a comprehensive computational study on the reactions of secondary ozonide (SOZ) with ammonia and water molecules. The mechanisms were studied in both a vacuum and the aqueous medium. All the molecular geometries were optimized using the B3LYP functional in conjunction with several basis sets. M06-2X, APFD, and ωB97XD functionals with the full basis set were also used. In addition, single-point energy calculations were performed with the G4MP2 and G3MP2 methods. Five different mechanistic pathways were studied for the reaction of SOZ with ammonia and water molecules. The most plausible mechanism for the reaction of SOZ with ammonia yields HC(O)OH, NH3, and HCHO as products, with ammonia herein acting as a mediator. This pathway is exothermic and exergonic, with an overall barrier height of only 157 kJ mol−1 using the G3MP2 method. All the reaction pathways between SOZ and water molecules are endothermic and endergonic reactions. The most likely reaction pathway for the reaction of SOZ with water involves a water dimer, in which the second water molecule acts as a mediator, with an overall barrier height of only 135 kJ mol−1 using the G3MP2 method. Solvent effects were found to incur a significant reduction in activation energies. When the second H2O molecule acts as a mediator in the reaction of SOZ with water, the barrier height of the rate-determining step state decreases significantly.

Quantum chemical study on the atmospheric photooxidation of ethyl acetate

2014 ◽  
Vol 92 (9) ◽  
pp. 814-820 ◽  
Author(s):  
Yan Zhao ◽  
Xiaomin Sun ◽  
Wenxing Wang ◽  
Laixiang Xu
Keyword(s):  
Acetic Anhydride ◽  
Ethyl Acetate ◽  
Density Functional ◽  
Single Point ◽  
Quantum Chemical Study ◽  
Density Functional Theory Method ◽  
Basis Set ◽  
Oh Radicals ◽  
Point Energy ◽  
Rearrangement Reaction

The mechanism for OH radical initiated atmospheric photoxidation reaction of ethyl acetate was carried out by using the density functional theory method. Geometries have been optimized at the B3LYP level with a standard 6-31G(d,p) basis set. The single-point energy calculations have been performed at the MP2/6-31G(d), MP2/6-311++G(d,p), and CCSD(T)/6-31G(d) levels, respectively. All of the possible degradation channels involved in the oxidation of ethyl acetate by OH radicals have been presented and discussed. Among the five possible hydrogen abstraction pathways of the reaction of ethyl acetate with OH radicals, the hydrogen abstractions from the C1–H3 and C2–H5 bonds are the dominant reaction pathways due to the low potential barriers and strong exothermicity. The β-ester rearrangement of IM6 is energetically favorable but is not expected to be important. The α-ester rearrangement reaction and O2 direct abstraction from IM17 are the more favorable pathways and are strongly competitive. In addition, the α-ester rearrangement reaction is confirmed to be a one-step process. Acetic acid, formic acetic anhydride, acetoxyacetaldehyde, and acetic anhydride are the main products for the reaction of ethyl acetate with OH radicals.

Theoretical study on the reaction mechanism of vinyl acetate with OH radicals in the atmosphere

2013 ◽  
Vol 91 (4) ◽  
pp. 241-247 ◽  
Author(s):  
Yan Zhao ◽  
Haitao Sun ◽  
Renjun Wang ◽  
Fei Gao
Keyword(s):  
Vinyl Acetate ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Theoretical Study ◽  
Single Point ◽  
Density Functional Theory Method ◽  
Basis Sets ◽  
Stationary Points ◽  
Oh Radicals ◽  
Point Energy

The reaction mechanisms of vinyl acetate with OH radicals in the atmosphere have been studied using the density functional theory method. The geometry parameters and frequencies of all of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis sets. The single-point energy calculations are carried out at the MPWB1K/6-311+G(3df,2pd) level. The detailed profiles of the potential energy surfaces for the reactions are constructed. Two OH addition and three H abstraction reaction pathways are considered for the reaction of vinyl acetate with OH radicals. The theoretical study shows that the most energetically favorable isomer is that of OH addition to the terminal carbon positions (C1 atom). The α-ester rearrangement, which is characteristic of ester oxidation processes, is confirmed to be thermodynamically and kinetically favorable. The main products of the OH-initiated atmospheric oxidation of vinyl acetate are formaldehyde, formic acetic anhydride, and acetic acid.

scholarly journals Direct Kinetic Measurements and Master Equation Modelling of the Unimolecular Decomposition of Resonantly-Stabilized CH2CHCHC(O)OCH3 Radical and an Upper Limit Determination for CH2CHCHC(O)OCH3 + O2 Reaction

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1251-1268 ◽  
Author(s):  
Satya Prakash Joshi ◽  
Prasenjit Seal ◽  
Timo Theodor Pekkanen ◽  
Raimo Sakari Timonen ◽  
Arrke J. Eskola
Keyword(s):  
Master Equation ◽  
Density Functional ◽  
Rate Coefficient ◽  
Decomposition Kinetics ◽  
Basis Sets ◽  
Stationary Points ◽  
Unimolecular Decomposition ◽  
Kinetic Measurements ◽  
Point Energy ◽  
Upper Limit

AbstractMethyl-Crotonate (MC, (E)-methylbut-2-enoate, CH3CHCHC(O)OCH3) is a potential component of surrogate fuels that aim to emulate the combustion of fatty acid methyl ester (FAME) biodiesels with significant unsaturated FAME content. MC has three allylic hydrogens that can be readily abstracted under autoignition and combustion conditions to form a resonantly-stabilized CH2CHCHC(O)OCH3 radical. In this study we have utilized photoionization mass spectrometry to investigate the O2 addition kinetics and thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical. First we determined an upper limit for the bimolecular rate coefficient of CH2CHCHC(O)OCH3 + O2 reaction at 600 K (k ≤ 7.5 × 10−17 cm3 molecule−1 s−1). Such a small rate coefficient suggest this reaction is unlikely to be important under combustion conditions and subsequent efforts were directed towards measuring thermal unimolecular decomposition kinetics of CH2CHCHC(O)OCH3 radical. These measurements were performed between 750 and 869 K temperatures at low pressures (<9 Torr) using both helium and nitrogen bath gases. The potential energy surface of the unimolecular decomposition reaction was probed at density functional (MN15/cc-pVTZ) level of theory and the electronic energies of the stationary points obtained were then refined using the DLPNO-CCSD(T) method with the cc-pVTZ and cc-pVQZ basis sets. Master equation simulations were subsequently carried out using MESMER code along the kinetically important reaction pathway. The master equation model was first optimized by fitting the zero-point energy corrected reaction barriers and the collisional energy transfer parameters $\Delta{E_{{\text{down}},\;{\text{ref}}}}$ and n to the measured rate coefficients data and then utilize the constrained model to extrapolate the decomposition kinetics to higher pressures and temperatures. Both the experimental results and the MESMER simulations show that the current experiments for the thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical are in the fall-off region. The experiments did not provide definite evidence about the primary decomposition products.

Quantum-Chemical Ab Initio Calculations on Inda- and Thallabenzene (C5H5In and C5H5Tl) and their Structural Isomers η5-C5H5In and η5-C5H5Tl

2018 ◽  
Vol 71 (3) ◽  
pp. 102
Author(s):  
Emma Persoon ◽  
Yuekui Wang ◽  
Gerhard Raabe
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Density Functional ◽  
Single Point ◽  
Normal Modes ◽  
Dft Method ◽  
Basis Sets ◽  
Triplet States ◽  
Structural Isomers ◽  
Td Dft

Quantum-chemical ab initio, time-independent, as well as time-dependent density functional theory (TD-DFT) calculations were performed on the so far elusive heterocycles inda- and thallabenzene (C5H5In and C5H5Tl), employing several different methods (MP2, CISD, CCSD, CCSD(T), BD, BD(T), QCISD, QCISD(T), CASSCF, DFT/B3LYP), effective core potentials, and different basis sets. While calculations on the MP2 level predict the ground states of the title compounds to be singlets with the first triplet states between 13 and 15 kcal mol−1 higher in energy, single point calculations with the QCISD(T), CCSD(T), and BD(T) methods at CCSD-optimized structures result in energy differences between the singlet and the triplet states in the range between 0.3 and 2.1 kcal mol−1 in favour of the triplet states. According to a CASSCF(8,8) calculation the triplets are also more stable by about 2.5–2.9 kcal mol−1. Calculations were also performed for the C5v-symmetric η5 structural isomers (cyclopentadienylindium, CpIn, and cyclopentadienylthallium, CpTl, Cp = C5H5) of the title compounds. At the highest level of theory employed in this study, C5H5In is between 79 and 88 kcal mol−1 higher in energy than CpIn, while this energy difference is even larger for thallabenzene where C5H5Tl is energetically between 94 and 102 kcal mol−1 above CpTl. In addition we report on the UV/vis spectra calculated with a TD-DFT method as well as on the spectra of the normal modes of C5H5In and C5H5Tl. Both types of spectra might facilitate identification of the title compounds eventually formed in photolysis or pyrolysis experiments.

scholarly journals Structural, Electronic, and Vibrational Properties of Isoniazid and Its Derivative N-Cyclopentylidenepyridine-4-carbohydrazide: A Quantum Chemical Study

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Anoop kumar Pandey ◽  
Abhishek Bajpai ◽  
Vikas Baboo ◽  
Apoorva Dwivedi
Keyword(s):  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Basis Sets ◽  
Ground State Structure ◽  
Vibrational Modes ◽  
Functional Theory ◽  
Complete Assignment ◽  
Experimental Values ◽  
Homo Lumo

Isoniazid (Laniazid, Nydrazid), also known as isonicotinylhydrazine (INH), is an organic compound that is the first-line medication in prevention and treatment of tuberculosis. The optimized geometry of the isoniazid and its derivative N-cyclopentylidenepyridine-4-carbohydrazide molecule has been determined by the method of density functional theory (DFT). For both geometry and total energy, it has been combined with B3LYP functionals having LANL2DZ and 6-311 G (d, p) as the basis sets. Using this optimized structure, we have calculated the infrared wavenumbers and compared them with the experimental data. The calculated wavenumbers by LANL2DZ are in an excellent agreement with the experimental values. On the basis of fully optimized ground-state structure, TDDFT//B3LYP/LANL2DZ calculations have been used to determine the low-lying excited states of isoniazid and its derivative. Based on these results, we have discussed the correlation between the vibrational modes and the crystalline structure of isoniazid and its derivative. A complete assignment is provided for the observed FTIR spectra. The molecular HOMO, LUMO composition, their respective energy gaps, and MESP contours/surfaces have also been drawn to explain the activity of isoniazid and its derivative.

HYDRATION AND DISSOCIATION OF CALCIUM HYDROXIDE IN WATER CLUSTERS: A QUANTUM CHEMICAL STUDY

2007 ◽  
Vol 06 (03) ◽  
pp. 595-609 ◽  
Author(s):  
CLARA JIAYUN MEN ◽  
FU-MING TAO
Keyword(s):  
Calcium Hydroxide ◽  
Quantum Chemical ◽  
Density Functional ◽  
Water Clusters ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Structure Stability ◽  
Water Molecules ◽  
Aerosol Formation ◽  
Hydrated Clusters

The structure, stability, and properties of the hydrated clusters of calcium hydroxide, Ca ( OH )2( H 2 O )n, n = 1–6, were investigated using density functional and ab initio quantum chemical methods. The results show that six water molecules are needed to result in the complete dissociation of Ca ( OH )2. The stable and ionic conformer of Ca ( OH )2( H 2 O )6 has C 3 symmetry. Its surprising stability and high IR activity render hydrated clusters of Ca ( OH )2 potentially significant in the nucleation of noctilucent clouds in the mesosphere. Trends in the interaction energies (ΔEe) of the complexes show that water molecules in the first shell of Ca 2+ are highly stable, further alluding to the role of hydrated Ca ( OH )2 in aerosol formation.

Atmospheric oxidation mechanism of polyfluorinated sulfonamides — A quantum chemical and kinetic study

2013 ◽  
Vol 91 (6) ◽  
pp. 472-478 ◽  
Author(s):  
Xiaoyan Sun ◽  
Lei Ding ◽  
Qingzhu Zhang ◽  
Wenxing Wang
Keyword(s):  
Rate Constants ◽  
Density Functional ◽  
Single Point ◽  
Oxidation Mechanism ◽  
Basis Set ◽  
Atmospheric Oxidation ◽  
Oh Radicals ◽  
Oh Radical ◽  
Orbital Theory ◽  
Point Energy

Polyfluorinated sulfonamides (FSAs, F(CF2)nSO2NR1R2) are present in the atmosphere and may serve as the source of perfluorocarboxylates (PFCAs, CF3(CF2)nCOO–) in remote locations through long-range atmospheric transport and oxidation. Density functional theory (DFT) molecular orbital theory calculations were carried out to investigate OH radical-initiated atmospheric oxidation of a series of sulfonamides, F(CF2)nSO2NR1R2 (n = 4, 6, 8). Geometry optimizations of the reactants as well as the intermediates, transition states, and products were performed at the MPWB1K level with the 6-31G+(d,p) basis set. Single-point energy calculations were carried out at the MPWB1K/6-311+G(3df,2p) level of theory. The OH radical-initiated reaction mechanism is given and confirms that the OH addition to the sulfone double bond producing perfluoroalkanesulfonic acid directly cannot occur in the general atmosphere. Canonical variational transition-state (CVT) theory with small curvature tunneling (SCT) contribution was used to predict the rate constants. The overall rate constants were determined, k(T) (N-EtFBSA + OH) = (3.21 × 10−12) exp(–584.19/T), k(T) (N-EtFHxSA + OH) = (3.21 × 10−12) exp(–543.24/T), and k(T) (N-EtFOSA + OH) = (2.17 × 10−12) exp(–504.96/T) cm3 molecule−1 s−1, over the possible atmospheric temperature range of 180–370 K, indicating that the length of the F(CF2)n group has no large effect on the reactivity of FSAs. Results show that the atmospheric lifetime of FSAs determined by OH radicals will be 20–40 days, which agrees well with the experimental values (20–50 days), 20 thus they may contribute to the burden of perfluorinated pollution in remote regions.

Quantum chemical study of inner-sphere complexes of trivalent lanthanide and actinide ions on the corundum (0001) surface

2010 ◽  
Vol 98 (9-11) ◽  
pp. 627-634 ◽  
Author(s):  
Robert Polly ◽  
Bernd Schimmelpfennig ◽  
Thomas Rabung ◽  
Mathias Flörsheimer ◽  
Reinhardt Klenze ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Trivalent Lanthanide ◽  
Inner Sphere ◽  
Actinide Ions ◽  
Inner Sphere Complexes

scholarly journals Comparison of computational chemistry methods for the discovery of quinone-based electroactive compounds for energy storage

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Qi Zhang ◽  
Abhishek Khetan ◽  
Süleyman Er
Keyword(s):  
Energy Storage ◽  
Prediction Accuracy ◽  
Density Functional ◽  
Single Point ◽  
Computational Cost ◽  
Systematic Evaluation ◽  
Redox Potentials ◽  
Implicit Solvation ◽  
Point Energy ◽  
Computational Screening

AbstractHigh-throughput computational screening (HTCS) is a powerful approach for the rational and time-efficient design of electroactive compounds. The effectiveness of HTCS is dependent on accuracy and speed at which the performance descriptors can be estimated for possibly millions of candidate compounds. Here, a systematic evaluation of computational methods, including force field (FF), semi-empirical quantum mechanics (SEQM), density functional based tight binding (DFTB), and density functional theory (DFT), is performed on the basis of their accuracy in predicting the redox potentials of redox-active organic compounds. Geometry optimizations at low-level theories followed by single point energy (SPE) DFT calculations that include an implicit solvation model are found to offer equipollent accuracy as the high-level DFT methods, albeit at significantly lower computational costs. Effects of implicit solvation on molecular geometries and SPEs, and their overall effects on the prediction accuracy of redox potentials are analyzed in view of computational cost versus prediction accuracy, which outlines the best choice of methods corresponding to a desired level of accuracy. The modular computational approach is applicable for accelerating the virtual studies on functional quinones and the respective discovery of candidate compounds for energy storage.

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