scholarly journals Electronic Structure and Physical-Chemistry Property Relationship for Oxazole Derivatives by Ab Initio and DFT Methods

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
Salah Belaidi ◽  
Malika Mellaoui
Keyword(s):  
Physical Chemistry ◽  
Electronic Structure ◽  
Ab Initio ◽  
Dipole Moments ◽  
Electron Affinities ◽  
Dft Theory ◽  
Dft Methods ◽  
Net Charges ◽  
Ab Initio And Dft ◽  
Oxazole Derivatives

The geometric, electronic structure, effect of the substitution, and structure physical-chemistry relationship for oxazoles derivatives have been studied by ab initio and DFT theory. In the present work, the calculated values, namely, net charges, bond lengths, dipole moments, electron affinities, heats of formation, and QSAR properties are reported and discussed in terms of the reactivity of oxazole derivatives.

Ab initio and DFT theory studies of interaction of thymine with formaldehyde

2008 ◽  
Vol 19 (5) ◽  
pp. 843-847 ◽  
Author(s):  
Cheng Yang ◽  
Haijun Wang
Keyword(s):  
Ab Initio ◽  
Dft Theory ◽  
Ab Initio And Dft

Theoretical study of the adsorption of isobutane over H-mordenite zeolite by ab initio and DFT methods

2003 ◽  
Vol 200 (1-2) ◽  
pp. 205-212 ◽  
Author(s):  
L.A Garcı́a-Serrano ◽  
C.A Flores-Sandoval ◽  
I.P Zaragoza
Keyword(s):  
Ab Initio ◽  
Theoretical Study ◽  
Dft Methods ◽  
Ab Initio And Dft

scholarly journals Динамические поляризуемости двухатомных молекул: сравнение методов ab initio и теории функционала плотности с методом замещенной функции Грина теории квантового дефекта

2019 ◽  
Vol 127 (11) ◽  
pp. 736
Author(s):  
А.С. Корнев ◽  
К.И. Суворов ◽  
В.Е. Чернов ◽  
И.В. Копытин ◽  
Б.А. Зон
Keyword(s):  
Ab Initio ◽  
Excited States ◽  
Density Functional ◽  
Ab Initio Methods ◽  
Test Results ◽  
Dft Methods ◽  
Functional Theory ◽  
Frequency Dependent ◽  
Quantum Defect Theory ◽  
Ab Initio And Dft

The quantum defect theory is used to test the accuracy of ab initio methods and density functional theory (DFT) in calculating the frequency-dependent polarizabilities of diatomic molecules. We confine ourselves to testing only those variants of these methods that are most accurate for calculating static polarizabilities. The test results show that one of the main errors of the ab initio and DFT methods is associated with inaccuracies in determining the energies of excited states, where frequency-dependent polarizabilities have resonance maxima.

scholarly journals Electronic Structure Benchmark Calculations of CO2 Fixing Elementary Chemical Steps in RuBisCO Using the Projector-Based Embedding Approach

2020 ◽  
Author(s):  
Oscar A. Douglas-Gallardo ◽  
Ian J. Shepherd ◽  
Simon Bennie ◽  
Kara Ranaghan ◽  
Adrian Mulholland ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Atmospheric Carbon Dioxide ◽  
Density Functional ◽  
Enzyme Reaction ◽  
Dft Methods ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
Carbon Carbon Bond ◽  
Reaction Energies

<div>Ribulose 1,5-bisphosphate carboxylase-oxygenase (RuBisCO) is the main enzyme involved in atmospheric carbon dioxide (CO<sub>2</sub>) fixation in the biosphere. This enzyme catalyses a set of five chemical steps that take place in the same active-site within magnesium (II) coordination sphere. Here, a set of electronic structure benchmark calculations have been carried out on a reaction path proposed by Gready <i>et al.</i> by means of the projector-based embedding approach. Activation and reaction energies for all main steps catalyzed by RuBisCO have been calculated at the MP2, SCS-MP2, CCSD and CCSD(T)/aug-cc-pVDZ and cc-pVDZ levels of theory. </div><div><br></div><div>The treatment of the magnesium cation with post-HF methods is explored to determine the nature of its involvement in the mechanism. With the high-level ab initio values as a reference, we tested the performance of a set of density functional theory (DFT) exchange-correlation (xc) functionals in reproducing the reaction energetics of RuBisCO carboxylase activity on a set of model fragments. Different DFT xc-functionals show large variation in activation and reaction energies. Activation and reaction energies computed at the B3LYP level are close to the reference SCS-MP2 results for carboxylation, hydration and protonation reactions.</div><div><br></div><div>However, for the carbon-carbon bond dissociation reaction, B3LYP and other functionals give results that differ significantly from the ab initio reference values. The results show the applicability of the projector-based embedding approach to metalloenzymes. This technique removes the uncertainty associated with the selection of different DFT xc-functionals and so can overcome some of inherent limitations of DFT calculations, complementing and potentially adding to modelling of enzyme reaction mechanisms with DFT methods.</div>

scholarly journals Novel organic material with potential NLO application - electronic and spectroscopic properties

2008 ◽  
Vol 6 (4) ◽  
pp. 592-599 ◽  
Author(s):  
B.B. Koleva ◽  
T. Kolev ◽  
R. Nikolova ◽  
Y. Zagraniarsky ◽  
M. Spiteller
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Ir Spectroscopy ◽  
Ab Initio ◽  
Organic Material ◽  
Spectroscopic Properties ◽  
Thermal Methods ◽  
Polarized Ir Spectroscopy ◽  
Cosy Nmr ◽  
Ab Initio And Dft

AbstractNovel dicyanoisophorone derivative, (E)-2-(3-(4-aminostyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile, is synthesized and its structure elucidated by means of conventional and linear polarized IR-spectroscopy of oriented colloids in nematic host, 1H, 13C, 1H, 1H-COSY NMR, HPLC tandem ESI MS-MS spectrometry, UV-VIS and thermal methods. Ab initio and DFT level of theory are used to theoretically obtain the electronic structure and optical properties, both in ground and exited state, of the compound.

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