nowadays nmr spectroscopy becomes a powerful tool in chemistry because of the nmr chemical shifts. hartree–fock theory and the gauge-including atomic orbital (giao) methods are used in the calculation of 29si nmr chemical shifts of various silicate species in the silicate solution as initial components for zeolite synthesis both in gas and solution phase. calculations have been performed at geo...

We present the gauge invariant atomic orbital ~GIAO! calculation of nuclear magnetic shieldings for solvated molecules described within the polarizable continuum model ~PCM!. The performance of the PCM-GIAO approach is tested in a benchmark calculation of isotropic C, N, and O shielding constants for CH3CN and CH3NO2 in vacuo and in water, both at the Hartree–Fock and density functional levels ...

Density Functional Theory (DFT) calculations at the B3LYP/6-31+G∗ level have been performed on 5-thiabicyclo[2.1.1]hex-2-ene S-oxide derivatives. The geometrical and electronic properties of the compounds have been analyzed in order to explain the favored stability of the exo configuration. Isodesmic reactions at the Gaussian-G2 theory yielded the exo conformer as the most stable one. Moreover,...

Pinus krempfii Lecomte (Pinaceae) is an endemic tree to Vietnam with restricted habitats at higher altitudes in the highlands. In this study, genetic variation of four populations of P. krempfii was assessed using 17 microsatellite markers (single sequence repeats). Of these 17 markers, eight were polymorphic, and among the 42 putative alleles amplified, 32 were polymorphic (accounting for 76.1...

Nowadays NMR spectroscopy becomes a powerful tool in chemistry because of the NMR chemical shifts. Hartree–Fock theory and the Gauge-including atomic orbital (GIAO) methods are used in the calculation of 29Si NMR chemical shifts of various silicate species in the silicate solution as initial components for zeolite synthesis both in gas and solution phase. Calculations have been performed at geo...

The boronium-carbonium ion continuum was extended to include hypercoordinated onium-carbonium dications and the isoelectronic onium-boronium cation analogs. Structures and (13)C and (11)B NMR chemical shifts of the onium-carbonium dications and the corresponding isoelectronic and isostructural onium-boronium cations were calculated with the ab initio/GIAO-MP2 method. The data show a good linear...

Isotropic H and C nuclear magnetic shielding constants of enantiometrically pure 1-trifluoromethyl tetrahydroisoquinoline alkaloids have been calculated by employing the gauge-including-atomic-orbital (GIAO) method at the B3LYP density functional level of theory. Geometry of each compound has been optimized employing 6-31G(d,p) and 6-311G basis sets. The theoretical trends are compared with exp...

The structures of core-links Al(13) (C-Al(13)) and flat-Al(13) (F-Al(13)) complexes in aqueous solution have been investigated using density functional theory (DFT) at the level of B3LYP/6-31G(d). The present work focuses on the following three aspects: (1) C-Al(13)(9+) was optimized with the consideration of solvent effect and the (27)Al NMR chemical shifts using Hartree Fock GIAO and B3LYP GI...

A current-density functional theory for the calculation of nuclear magnetic resonance chemical shifts is presented. If the Kohn–Sham orbitals are expanded in a finite basis set, one of the main problems is the strong dependency of the results with respect to a shift of the gauge origin of the vector potential which describes the external magnetic field. Two computational schemes implementing bo...