hartree-fock (hf) and density functional theory (dft) methods employed to study the effect of conformational change on the 13c chemical shifts of 6-mono axial and equatorial substituted and 6,7-di axial-axial, equatorial-equatorial and axial-equatorial substitutedderivatives of 5,6,7,8-tetrahydrodibenzo[a,c]cyclo-octene. the geometry of the conformers have been optimized in the gas phase employ...

Hartree-Fock (HF) and Density Functional Theory (DFT) methods employed to study the effect of conformational change on the 13C chemical shifts of 6-mono axial and equatorial substituted and 6,7-di axial-axial, equatorial-equatorial and axial-equatorial substitutedderivatives of 5,6,7,8-tetrahydrodibenzo[a,c]cyclo-octene. The geometry of the conformers have been optimized...

The sources of error in the calculation of nuclear-magnetic-resonance shielding constants determined by density-functional theory are examined. Highly accurate Kohn-Sham wave functions are obtained from coupled-cluster electron density functions and used to define accurate-but current independent-density-functional shielding constants. These new reference values, in tandem with high-accuracy co...

Reduction of the two "closed" [6,6] methanofullerenes, [6,6]C(61)H(2) (1) and [6,6]C(71)H(2) (5), to the corresponding hexaanions with lithium metal causes the bridgehead-bridgehead bonds to open, at least partially, and this change gives rise to diamagnetic ring currents in the resulting homoconjugated six-membered rings (6-MRs). These new ring currents shield the overlying hydrogen atoms on t...

The Cover Feature shows how the change in balance between diamagnetic and paramagnetic contributions to shielding benzene cyclobutadiene leads overall distributions characteristic of aromatic antiaromatic molecules, respectively. More information can be found Research Article by Peter B. Karadakov.

A method to approximate ab initio shielding constants is presented, in which the ab initio density matrix is replaced in the gauge invariant atomic orbital formalism with the density matrix resulting from an effective fragment potential calculation. The resulting first-order density matrix is then iterated to self-consistency. The method is compared with fully ab initio gauge invariant atomic o...

The notion of formal atomic charges in molecules is probably the most debated issue in quantum chemistry. Although atomic charge can not be rigorously defined in a unique way, conclusive evidence is given here which shows that it provides semiquantitative information about a number of molecular properties in a very simple and transparent way. In particular, the calculations of ESCA chemical shi...

D. Direct Nuclear Spin-Spin Interactions in Free Molecules. Internuclear Spacings and Shapes of Molecular Vibrational Potential IS. Direct Nuclear Spin-Spin Interactions in Rigid Solids. Atomic Spacings and Bond Angles F. Nuclear Paramagnetic Resonance Line Widths in Liquids and Gases Collision Narrowing G. The Effect of Nuclear Motion on Nuclear Resonance Spectra in Crystals. Hindered Rotatio...

Density functional theory (DFT) calculations of the magnetic shielding for solid state nuclear magnetic resonance (NMR) provide an important contribution for the understanding of experimentally observed signals. In this work, we present calculations of the Y NMR shielding in intermetallic compounds (YMg, YT, YTX, YT2X, YT2X2, Y2TB6, and Y2TSi3 where T represents various transition metals and X ...