نتایج جستجو برای: b3lyp

تعداد نتایج: 3756  

Journal: :Journal of molecular modeling 2009
Amar Saal Claude August Daul Thibaut Jarrosson Ourida Ouamerali

A set of supramolecular cage-structures--spherophanes--was studied at the density functional B3LYP level. Full geometrical structure optimisations were made with 6-31G and 6-31G(d) basis sets followed by frequency calculations, and electronic energies were evaluated at B3LYP/6-31++G(d,p). Three different symmetries were considered: C1, Ci, and Oh. It was found that the bonds between the benzene...

2011
Joanna E. Rode Jan Cz. Dobrowolski Joanna Sadlej

The conformational landscape of phenylisoserine (PhIS) was studied. Trial structures were generated by allowing for all combinations of single-bond rotamers. Based on the B3LYP/aug-cc-pVDZ calculations 54 conformers were found to be stable in the gas phase. The six most stable conformers were further optimized at the B3LYP/aug-cc-pVTZ and MP2/aug-cc-pVDZ levels for which characteristic intramol...

2013
Dominik Walczak Andrzej Nowacki

B3LYP/6-31+G level computations were performed for the formation of four trimethylammonium salts in the reaction of methyl chloride (1a), (S)-1,4-andydro-5-chloro-2,3,5-trideoxypentitol (2a), (2S,5S)-2,5-andydro-6-chloro-1,3,4,6-tetradeoxyhexitol (3a) and methyl 5-chloro-2,3,5-trideoxy-β-D-pentofuranoside (4a) with trimethylamine. All the structures were fully optimized in the gas phase, in chl...

1997
Tim P. W. Jungkamp John H. Seinfeld

The complete basis set model chemistries CBS-4 and CBS-q were modified using density functional theory for the geometry optimization step of these methods. The accuracy of predicted bond dissociation energies and transition state barrier heights was investigated based on geometry optimizations using the B3LYP functional with basis set sizes ranging from 3-21G(d ,p) to 6-311G(d ,p). Transition s...

Journal: :The journal of physical chemistry. A 2005
Lisa Pollack Theresa L Windus Wibe A de Jong David A Dixon

The heats of formation for the n-alkanes C(n)H(n+2) for n = 5, 6, and 8 have been calculated using ab initio molecular orbital theory. Coupled-cluster calculations with perturbative triples (CCSD(T)) were employed for the total valence electronic energies. Correlation-consistent basis sets were used, up through the augmented quadruple zeta, to extrapolate to the complete basis set limit. Geomet...

Journal: :The journal of physical chemistry. A 2014
Bishnu Thapa H Bernhard Schlegel

Experimental studies by Yamanouchi and co-workers indicate that an intense 40 fs 800 nm laser pulse can cause CH3OH(+) to isomerizes during the pulse. The potential energy surfaces of methanol neutral, monocation, and singlet and triplet dication were explored using the CBS-APNO, CBS-QB3, CAM-B3LYP, and B3LYP levels of theory. Ab initio classical trajectories were calculated in the presence of ...

Journal: :Magnetic resonance in chemistry : MRC 2007
Keith W Wiitala Christopher J Cramer Thomas R Hoye

Full (1)H and (13)C NMR chemical shift assignments were made for two sets of penam beta-lactams: namely, the diastereomeric (2S, 5S, 6S)-, (2S, 5R, 6R)-, (2S, 5S, 6R)-, and (2S, 5R, 6S)-methyl 6-(1,3-dioxoisoindolin-2-yl)-3,3-dimethyl-7-oxo-4-thia-1-aza-bicyclo[3.2.0]heptane-2-carboxylates (1-4) and (2S, 5R, 6R)-, (2S, 5S, 6R)-, and (2S, 5R, 6S)-6-(1,3-dioxoisoindolin-2-yl)-3,3-dimethyl-7-oxo-4...

Journal: :Physical chemistry chemical physics : PCCP 2007
Elizabeth Rincón Manuel Yáñez Alejandro Toro-Labbé Otilia Mó

The effect of Ni(II), Cu(II) and Zn(II) association on the diketo/keto-enol tautomerism of thymine has been investigated through the use of B3LYP density functional theory calculations. Final energies were obtained at the B3LYP/6-311+G(2df,2p)//B3LYP/6-311+G(d,p) level of theory. Ni(II) and Cu(II) lead to an oxidation of thymine which for Zn(ii) is only partial and catalyze the tautomerization ...

Journal: :Acta chimica Slovenica 2011
Haomiao Zhang Tanzhang Chen Yingying Yu Shi Wu

The relative stabilities of the nine possible isomers for C80O based on C80(D5d) were investigated via density function theory (DFT) at B3LYP/6-31G(d) level. The most stable geometry of C80O is predicted to be 23,24-C80O, where an annulene-like structure is formed. The stretching vibration frequencies of the C=C bonds in the IR spectrum of C80O compared with those of the C=C bonds in the IR spe...

2009
Sue Y. Bae Mark D .Winemiller Fu-Lian Hsu Dennis K. Rohrbaugh Harold D. Banks

Degradation products that could reasonably form upon storage of sulfur mustard have been synthesized and analyzed by GC/MS. Elucidation of the fragmentation pathways was accomplished by means of B3LYP/6-31+G(d) calculations.

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