In this work, 242 NMR spin–spin coupling constants (SSCC) in 20 molecules are calculated, either with correlated wave function methods, SOPPA and HRPA(D), or density functional theory based on the B3LYP, BHandH, PBE0 functionals. The calculations were carried out without treatment of solvation via a polarizable continuum model both geometry optimization step and/or SSCC calculation, thereby, fo...

Correlated ab initio wave function calculations using MP2/aug-cc-pVTZ model chemistry have been performed for three test sets of gas phase saccharide conformations to provide reference values for their relative energies. The test sets consist of 15 conformers of α- and β-d-allopyranose, 15 of 3,6-anhydro-4-O-methyl-d-galactitol, and four of β-d-glucopyranose. For each set, conformational energi...

Threshold collision-induced dissociation of M(+)(AAA) with Xe is studied using guided ion beam tandem mass spectrometry. M(+) include the alkali metal ions Na(+) and K(+). The three aromatic amino acids are examined, AAA = phenylalanine, tyrosine, or tryptophan. In all cases, endothermic loss of the intact aromatic amino acid is the dominant reaction pathway. The threshold regions of the cross ...

the density functional theory (dft) and the natural bond orbital (nbo) calculations basedmethod b3lyp/6-31g* were carried out to study the interaction of carbon nanotube (8,0) withnitrobenzene in two situations perpendicular and parallel. formation energies of compounds,charges, the highest occupied molecular orbital (homo) and the lowest unoccupied molecular'orbital (lumo) and the homo-lumo ba...

Density functional theory based calculations have been carried out to systematically investigate the structural and optoelectronic properties of pyridine-furan, pyridine-pyrrole and pyridine-thiophene oligomers. Comparison of results obtained at B3LYP/6-31G(d) and B3LYP-D3/6-31G(d) levels of theories reveals that the inclusion of dispersion correction with the B3LYP functional has a major impac...

We compute the absorption and emission energies and hence Stokes shifts of small diamondoids as a function of size using different theoretical approaches, including density-functional theory (DFT) and quantum Monte Carlo (QMC) calculations. The absorption spectra of these molecules are also investigated by time-dependent DFT and compared with experiment. We analyze the structural distortion and...

The conformational behavior and the structural stability of formyl fluoroketene, formyl chloroketene and formyl methylketene were investigated by utilizing quantum mechanical DFT calculations at B3LYP/6-31I + + G** and ab initio calculations at MP2/6-311 + + G** levels. The three molecules were predicted to have a planar s-cis<-->s-trans conformational equilibrium. From the calculations, the di...

The vibrational spectra of the electron donor–acceptor complex, tetracyanoethylene–perylene were measured at 4 K by inelastic neutron scattering (INS) using the filter analyzer neutron spectrometer (FANS) and at 20 K using the TOSCA instrument. A direct comparison of the measured spectrum was made to density functional calculations using the B3LYP/6-31G** treatment for the isolated complex, the...

Hydrogen atom transfer is one important reaction in biological system, industry, and atmosphere. The preluded by hydrogen bond dissociation. To gain a comprehensive understanding on the reaction, it necessary to investigate how current computational methods model As starting point, we utilized density functional theory-based calculations identify effect of dispersion long-range corrections O—H ...