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  • NMR chemical shifts  (2)
  • Theoretical, Physical and Computational Chemistry  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Investigation of Mössbauer parameters for a set of iodine compounds using gradient-corrected density functional theory (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 575-583 
    Details
    ISSN: 0020-7608
    Keywords: iodine compounds ; DFT ; Mössbauer ; isomer shifts ; nuclear quadrupole resonances ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present work we show the first application of density functional theory (DFT) with gradient-corrected exchange-correction functionals within the linear combination of Gaussian-type orbitals (LCGTO) formalism to the calculation of isomer shifts and quadrupole couplings for a large and varied set of iodine compounds: I2, ICl, IBr, ICN, HI, KI, CH3I, CH2I2, CHI3, CI4, SiI4, GeI4, and SnI4. The results are compared with experimental data from Mössbauer spectroscopy. The overall agreement with experiment is most satisfactory, with the exception of the highly dipolar systems ICl, IBr, and ICN. For these systems it is believed that the free molecule assumption of the calculations is not an entirely valid model of the crystalline environment of the experiments. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 575-583, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Solvent Effect on the NMR Chemical Shieldings in Water Calculated by a Combination of Molecular Dynamics and Density Functional Theory (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 452-457 
    Details
    ISSN: 0947-6539
    Keywords: density-functional theory ; liquid water ; molecular dynamics simulations ; NMR chemical shifts ; solvent effects ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solvent effect on the NMR chemical shielding in liquid water is calculated from a combination of molecular dynamics simulations and quantum chemical calculations for protons and 17O. The simulations are performed with three different potentials, ab initio as well as empirical ones, to study the influence of the force field. From the liquid configurations obtained in these simulations, molecules are randomly chosen together with neighbouring molecules to give clusters of water typical for the liquid at the selected temperature and density. Different cluster sizes are studied. The clusters are treated as supermolecules in quantum chemical calculations of chemical shifts by sum-over-states density functional perturbation theory with individual gauge for localised orbitals. The influence of the quantum chemical method is studied with an ab initio coupled Hartree-Fock gauge including atomic orbitals calculations with different basis sets for a selected cluster. An average over clusters yields the chemical shielding in the liquid at the selected temperature and density. The calculated values for the gas-liquid shift, which are in best agreement with experiment, are -3.2 ppm (exp. -4.26 ppm) for the proton and -37.6 ppm (exp. -36.1 ppm) for 17O, but the results depend strongly on the chosen interatomic potential.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020415
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  • 3
    Electronic Resource
    Electronic Resource
    Ab Initio ECP/DFT Calculation and Interpretation of Carbon and Oxygen NMR Chemical Shift Tensors in Transition-Metal Carbonyl ComplexesDedicated to Professor Paul von Ragué Schleyer on the occasion of his 65th birthday (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 24-30 
    Details
    ISSN: 0947-6539
    Keywords: density-functional theory ; NMR chemical shifts ; pseudopotentials ; relativistic effects ; transition-metal complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon and oxygen NMR chemical shift tensors for Group 6 hexacarbonyl complexes M(CO)6 (M = Cr, Mo, W) have been calculated by using a combination of quasirelativistic metal effective-core potentials and density-functional theory. Comparison with high-resolution solid-state shift tensors indicates excellent agreement between theory and experiment. The sensitivity of the shifts to the W-C distance in W(CO)6 is discussed. A breakdown of the shielding tensor components into contributions from localized molecular orbitals allows the detailed interpretation of the trends on going down Group 6, and of differences to free CO. Group trends in the carbon shielding tensors are related largely to contributions from M-C σ-bonding orbitals. The presence of occupied metal (n-1)p and (n-1)d orbitals is partly responsible for the changes on going from free to metalbound CO. The origin of the less pronounced trends in the oxygen shielding tensors is more complicated. The influence of scalar relativistic effects on the shift tensors has been studied for W(CO)6 and is found to be relatively small, in spite of considerable changes in the W-C distance.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020108
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    Paper (German National Licenses)
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