scholarly journals Study on the Mechanism of the Effect of Temperature on the Decomposition Reaction of SFn (n=1-6) under Discharge Conditions

2021 ◽  
Author(s):  
Minghao Yang ◽  
Jing Yan ◽  
Mengyuan Xu ◽  
Yingsan Geng ◽  
Zhiyuan Liu ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Electron Energy ◽  
Single Point ◽  
Zero Point ◽  
Decomposition Reaction ◽  
Chemical Kinetic ◽  
Effect Of Temperature ◽  
Thermal Decomposition Mechanism ◽  
Chemical Kinetic Model ◽  
Point Energy

Abstract The study on the mechanism of the effect of temperature on the decomposition reaction of SFn (n = 1–6) under discharge conditions is very important in studying the potential fault of SF6 high voltage switch equipment and perfecting the chemical kinetic model of SFn discharge. In this paper, structural optimizations, vibrational frequency calculations, and zero-point energy calculations for the reactants and products were performed at the B3LYP/6-311 + + G(d,p) theory level. The single-point energies of all species were collected at the CCSD(T)/aug-cc-PVTZ level. The electric and thermal decomposition mechanism of SFn under discharge conditions of 298K–10000K were studied, respectively. The conclusion drawn was that in the temperature range of 298–10000K, the thermal decomposition homopolytic reaction △G began to decline from 200 kJ/mol, while the △G of the other two heterogenous reactions began to decrease from 1000 kJ/mol and 2000 kJ/mol, showing a downward trend of an almost similar slope. The electrolysis of SFn is related to the electron energy. When the electron energy is low, SFn + e→SFn− series reactions occur, and △G of R12, R20, R28, R36, R44 increases with temperature rise, while △G of R4 decreases with temperature. When the electron energy is high, one of SFn−→SFn−1− + F、SFn−→SFn−1 + F− and SFn−→SFn−1 + F + e will occur, and the reactions that occur at various temperature ranges as the temperature rises vary. When the second electron hits the SFn−, the SFn− + e→SFn−1− + F reaction will occur. The △G of this reaction slowly decreases with an increase in temperature. This study in clearer terms explains the decomposition process and mechanism of SFn at different temperatures.

Predicting Carbonyl Excitation Energies Efficiently Using EOM-CC Trends

2020 ◽  
Author(s):  
Keiran Rowell ◽  
Scott Kable ◽  
Meredith J. T. Jordan
Keyword(s):  
Single Point ◽  
Zero Point ◽  
Tropospheric Chemistry ◽  
Excitation Energies ◽  
Relaxation Energy ◽  
Point Energy ◽  
Vertical Excitation ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Carbonyl Species

We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons) carbonyl species central to earth’s tropospheric chemistry. Triples contributions are needed for the vertical excitation energy (E<sup>vert</sup>), while EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S<sub>1</sub> relaxation energy (E<sup>relax</sup>), and (TD-)DFT suffices for the S<sub>0</sub> → S<sub>1</sub> zero-point vibration energy correction (∆E<sup>ZPVE</sup>). <div><br></div><div>Perturbative triples corrections deliver E<sup>vert</sup> values close in accuracy to full iterative triples EOM-CC calculations. The error between EOM-CCSD and triples-corrected E vert values appears to be systematic and can be accounted for with scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S<sub>0</sub> minima can be used to calculate E<sup>vert</sup> with negligible loss in accuracy, relegating the O(N<sup>5</sup>) expense of CCSD to only single-point energy and excitation calculations. </div><div><br></div><div>This affordable protocol can be applied to all volatile carbonyl species. E<sup>0−0</sup> predictions do overestimate measured values by ∼8 kJ/mol due to a lack of triples contribution in E relax, but this overestimation is systematic and the mean unsigned error is within 4 kJ/mol once this is accounted for.</div>

scholarly journals Predicting Carbonyl Excitation Energies Efficiently Using EOM-CC Trends

2020 ◽  
Author(s):  
Keiran Rowell ◽  
Scott Kable ◽  
Meredith J. T. Jordan
Keyword(s):  
Single Point ◽  
Zero Point ◽  
Tropospheric Chemistry ◽  
Excitation Energies ◽  
Relaxation Energy ◽  
Point Energy ◽  
Vertical Excitation ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Carbonyl Species

We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons) carbonyl species central to earth’s tropospheric chemistry. Triples contributions are needed for the vertical excitation energy (E<sup>vert</sup>), while EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S<sub>1</sub> relaxation energy (E<sup>relax</sup>), and (TD-)DFT suffices for the S<sub>0</sub> → S<sub>1</sub> zero-point vibration energy correction (∆E<sup>ZPVE</sup>). <div><br></div><div>Perturbative triples corrections deliver E<sup>vert</sup> values close in accuracy to full iterative triples EOM-CC calculations. The error between EOM-CCSD and triples-corrected E vert values appears to be systematic and can be accounted for with scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S<sub>0</sub> minima can be used to calculate E<sup>vert</sup> with negligible loss in accuracy, relegating the O(N<sup>5</sup>) expense of CCSD to only single-point energy and excitation calculations. </div><div><br></div><div>This affordable protocol can be applied to all volatile carbonyl species. E<sup>0−0</sup> predictions do overestimate measured values by ∼8 kJ/mol due to a lack of triples contribution in E relax, but this overestimation is systematic and the mean unsigned error is within 4 kJ/mol once this is accounted for.</div>

scholarly journals Predicting Carbonyl Excitation Energies Efficiently Using EOM-CC Trends

2020 ◽  
Author(s):  
Keiran Rowell ◽  
Scott Kable ◽  
Meredith J. T. Jordan
Keyword(s):  
Single Point ◽  
Zero Point ◽  
Tropospheric Chemistry ◽  
Excitation Energies ◽  
Relaxation Energy ◽  
Point Energy ◽  
Vertical Excitation ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Carbonyl Species

We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons) carbonyl species central to earth’s tropospheric chemistry. Triples contributions are needed for the vertical excitation energy (E<sup>vert</sup>), while EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S<sub>1</sub> relaxation energy (E<sup>relax</sup>), and (TD-)DFT suffices for the S<sub>0</sub> → S<sub>1</sub> zero-point vibration energy correction (∆E<sup>ZPVE</sup>). <div><br></div><div>Perturbative triples corrections deliver E<sup>vert</sup> values close in accuracy to full iterative triples EOM-CC calculations. The error between EOM-CCSD and triples-corrected E vert values appears to be systematic and can be accounted for with scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S<sub>0</sub> minima can be used to calculate E<sup>vert</sup> with negligible loss in accuracy, relegating the O(N<sup>5</sup>) expense of CCSD to only single-point energy and excitation calculations. </div><div><br></div><div>This affordable protocol can be applied to all volatile carbonyl species. E<sup>0−0</sup> predictions do overestimate measured values by ∼8 kJ/mol due to a lack of triples contribution in E relax, but this overestimation is systematic and the mean unsigned error is within 4 kJ/mol once this is accounted for.</div>

scholarly journals Molecular dynamics simulation of initial thermal decomposition mechanism of DNTF

2021 ◽  
Author(s):  
Hui Bai ◽  
Yiming Luo ◽  
Jun Jiang ◽  
Rui-jun Gou ◽  
Shuhai Zhang ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Thermal Decomposition ◽  
Early Stage ◽  
Decomposition Reaction ◽  
Carbon Chain ◽  
Chain Structure ◽  
Decomposition Mechanism ◽  
Dynamics Simulation ◽  
Energy Curve ◽  
Thermal Decomposition Mechanism

Abstract In order to understand the thermal decomposition characteristics of 3,4-Bis(3-nitrofurazan-4-yl)furoxan (DNTF), the thermal decomposition reaction of DNTF at 300-4000K temperature programmed and constant temperature of 2000K, 2500K, 3000K, 3500K and 4000K was simulated by ab initio computational molecular dynamics method. The thermal decomposition mechanism of DNTF at different temperatures was analyzed from the aspects of product evolution, cluster, potential energy curve and reaction path. The analysis of products, show that the initial small molecular products are NO, NO2, CO, CO2 and N2, and the final small molecular products are CO2 and N2. In the early stage, the ring-opening reaction of furoxan in DNTF structure is the main trigger reaction, and the C-C bond is broken at the initial stage of reaction. The carbon chain structure produced by decomposition forms various cluster structures in the form of C-N bond. In addition, it was found that temperature significantly affects the decomposition rate of DNTF, but does not change its initial decomposition path.

Quantum Chemistry Theoretical Studies on Molecular Structures of Polybutadiene

2009 ◽  
Vol 87-88 ◽  
pp. 130-133
Author(s):  
Ming Zhang ◽  
Zhi Xiong Huang ◽  
Min Xian Shi
Keyword(s):  
Molecular Weight ◽  
Quantum Chemistry ◽  
Function Theory ◽  
Single Point ◽  
Zero Point ◽  
Dft Method ◽  
Density Function Theory ◽  
Molecular Structures ◽  
Theoretical Studies ◽  
Point Energy

The Density Function Theory (DFT) method are employed to study the geometries of the polybutadiene （C4H6）n（n=3，4，5）on the base of B3LYP/6-311+G in the paper. the polybutadiene have five isomers, including Cis-1，4-polybutadiene, Trans-1, 4-polybutadiene, Isotactic1, 2-polybutadiene, Syndiotactic1，2-polybutadiene, Atactic1, 2-polybutadiene. The molecular structures of each isomer were evaluated on the basis of single point energy with zero point vibration correction. The results show that the energies of polybutadiene varied with increase of molecular weight.

Thermal Decomposition Kinetics of Glyphosate (GP) and its Metabolite Aminomethylphosphonic Acid (AMPA)

2019 ◽  
Author(s):  
Milad Narimani ◽  
Gabriel da Silva
Keyword(s):  
Thermal Decomposition ◽  
Reaction Rate ◽  
Decomposition Kinetics ◽  
Rate Theory ◽  
Thermal Decomposition Mechanism ◽  
Treatment Processes ◽  
Aminomethylphosphonic Acid ◽  
Reaction Rate Theory ◽  
Decomposition Chemistry ◽  
Kinetics Of

Glyphosate (GP) is a widely used herbicide worldwide, yet accumulation of GP and its main byproduct, aminomethylphosphonic acid (AMPA), in soil and water has raised concerns about its potential effects to human health. Thermal treatment processes are one option for decontaminating material containing GP and AMPA, yet the thermal decomposition chemistry of these compounds remains poorly understood. Here, we have revealed the thermal decomposition mechanism of GP and AMPA by applying computational chemistry and reaction rate theory methods. <br>

On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulations

2019 ◽  
Author(s):  
Riccardo Spezia ◽  
Hichem Dammak
Keyword(s):  
Degrees Of Freedom ◽  
Molecular Simulations ◽  
Zero Point ◽  
Thermal Bath ◽  
Unimolecular Dissociation ◽  
Point Energy ◽  
Rotational Degrees Of Freedom ◽  
The Difference ◽  
Nuclear Effects

<div> <div> <div> <p>In the present work we have investigated the possibility of using the Quantum Thermal Bath (QTB) method in molecular simulations of unimolecular dissociation processes. Notably, QTB is aimed in introducing quantum nuclear effects with a com- putational time which is basically the same as in newtonian simulations. At this end we have considered the model fragmentation of CH4 for which an analytical function is present in the literature. Moreover, based on the same model a microcanonical algorithm which monitor zero-point energy of products, and eventually modifies tra- jectories, was recently proposed. We have thus compared classical and quantum rate constant with these different models. QTB seems to correctly reproduce some quantum features, in particular the difference between classical and quantum activation energies, making it a promising method to study unimolecular fragmentation of much complex systems with molecular simulations. The role of QTB thermostat on rotational degrees of freedom is also analyzed and discussed. </p> </div> </div> </div>

scholarly journals The chemistry of cool circumstellar envelopes

1987 ◽  
Vol 122 ◽  
pp. 551-552
Author(s):  
L.A.M. Nejad ◽  
T. J. Millar
Keyword(s):  
Kinetic Model ◽  
Chemical Kinetic ◽  
Time Dependent ◽  
Circumstellar Envelopes ◽  
Chemical Kinetic Model ◽  
Ion Molecule Reactions ◽  
Cool Stars

We have developed a time-dependent chemical kinetic model to describe the chemistry in the circumstellar envelopes of cool stars, with particular reference to IRC + 10216. Our detailed calculations show that ion-molecule reactions are important in the formation of many of the species observed in IRC + 10216.

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