Ab Initio Studies on Amides: Pyrrolidin-2-one (γ-Butyrolactam)

1985 ◽  
Vol 38 (11) ◽  
pp. 1585 ◽  
Author(s):  
NV Riggs
Keyword(s):  
Ab Initio ◽  
Energy Cost ◽  
Equilibrium Structure ◽  
Ring Structure ◽  
Low Energy ◽  
Basis Set ◽  
Reference Plane ◽  
Envelope Conformation

By optimization with the 3-21G basis set, pyrrolidin-2-one is found clearly to prefer an envelope conformation with the flap bent 27.4° out of the NC(=O)C reference plane. The ring may be bent or twisted through a few degrees at low energy-cost, and undergoes rapid inversion through a planar-ring structure lying only 3.3 kJ mol-1 above the preferred equilibrium structure.

Assignment of the Low Energy Photoelectron Spectrum of the Octa-Sulphur Molecule: An ab initio Configuration Interaction Study

1983 ◽  
Vol 38 (12) ◽  
pp. 1359-1361 ◽  
Author(s):  
Michael H. Palmer
Keyword(s):  
Ab Initio ◽  
Configuration Interaction ◽  
Photoelectron Spectrum ◽  
Low Energy ◽  
Basis Set ◽  
Interaction Study ◽  
Orbital Ordering ◽  
Ionisation Potential ◽  
Koopmans Theorem ◽  
First Time

Abstract A large basis set ab initio configuration interaction study of S 8 has yielded a satisfactory assignment of the first 5 IP's of the UV-photoelectron spectrum for the first time. The ionisation potential order (low to high) is 2A1, 2E3, 2E2, 2E1 ≪2B2 and follows the orbital ordering of our recent large basis spd calculation, via the application of Koopmans' theorem.

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

Rotational de-excitations of C3H+ (1Σ+) by collision with He: new ab initio potential energy surface and scattering calculations

2020 ◽  
Vol 494 (4) ◽  
pp. 5675-5681 ◽  
Author(s):  
Sanchit Chhabra ◽  
T J Dhilip Kumar
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Ab Initio ◽  
Cross Sections ◽  
Energy Surface ◽  
Molecular Ions ◽  
Basis Set ◽  
Rate Coefficients ◽  
Close Coupling ◽  
Collisional Rate Coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

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.

Recycling lead from spent lead pastes using oxalate and sodium oxalate and preparation of novel lead oxide for lead-acid batteries

RSC Advances ◽  
2015 ◽  
Vol 5 (115) ◽  
pp. 94895-94902 ◽  
Author(s):  
Cheng Ma ◽  
Yuehong Shu ◽  
Hongyu Chen
Keyword(s):  
Energy Cost ◽  
Lead Oxide ◽  
Low Energy ◽  
Sodium Oxalate ◽  
Lead Acid Batteries ◽  
Smelting Method ◽  
Lead Acid

A sustainable method, with minimal pollution and low energy cost in comparison with the conventional smelting method, is proposed for treating components of spent lead acid batteries with oxalate and sodium oxalate.

Vicinal proton—proton coupling constants. Basis set dependence in SCF ab initio calculations

1993 ◽  
Vol 206 (1-4) ◽  
pp. 253-259 ◽  
Author(s):  
Jesús San-Fabián ◽  
Joaquín Guilleme ◽  
Ernesto Díez ◽  
Paolo Lazzeretti ◽  
Massimo Malagoli ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Coupling Constants ◽  
Basis Set ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton

Microwave Torch Plasmas for Decomposition of Gaseous Pollutants

2004 ◽  
Vol 7 (1) ◽  
Author(s):  
Mariusz Jasiński ◽  
Jerzy Mizeraczyk ◽  
Zenon Zakrzewski
Keyword(s):  
Atmospheric Pressure ◽  
Energy Cost ◽  
Gas Flow ◽  
Coaxial Line ◽  
Low Energy ◽  
Gaseous Pollutants ◽  
Gas Flow Rate ◽  
Torch Discharge ◽  
Volatile Organic ◽  
Moderate Power

AbstractResults of the study of decomposition of volatile organic compounds (VOCs including Freons) in their mixtures with either synthetic air or nitrogen, and nitrogen oxides NOx in their mixtures with N2 or Ar in low (~ 100 W) and moderate-power (200-400 W) microwave torch plasmas at atmospheric pressure are presented. Three types of microwave torch discharge (MTD) generators, i.e. the low-power coaxial-line-based MID, the moderate-power waveguide-based coaxial-line MTD and the moderate-power waveguide-based MTD generators were used. The gas flow rate and microwave power (2.45 GHz) delivered to the discharge were in the range of 1÷3 l/min and 100÷ 400 W, respectively. Concentrations of the processed gaseous pollutants usually were from several up to several tens percent. The energy efficiency of decomposition of several gaseous pollutants reached 1000 g/kWh. It was found that the microwave torch plasmas fully decomposed the pollutants at relatively low energy cost. This suggests that the MTD plasma can be a useful tool for decomposition of highly-concentrated gaseous pollutants.

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