Display options:
Normal
Show Abstracts
Compact
Displaying article 1-4
p. 28-38
Received: 5 July 2000 / Accepted: 21 August 2000 / Published: 23 August 2000
Show/Hide Abstract
| Download PDF Full-text (370 KB) Abstract: State-of-the-art molecular quantum chemical techniques have been applied to the solid-state compound Li2 CuO2 in order to derive accurate estimates of the in-chain magnetic interactions. In the present work, the magnitude of the nearest neighbour and next nearest neighbour magnetic coupling constants is investigated from first principles embedded cluster calculations. The convergence of the results is carefully tested for the cluster size. In contrast to the earlier findings, it is predicted that J2 is only ~15% of J1. In particular, it is shown that a large J2 appears when the Li+ ions are not explicitly included in the calculation.
p. 39-48
Received: 2 August 2000 / Accepted: 18 August 2000 / Published: 4 September 2000
Show/Hide Abstract
| Download PDF Full-text (50 KB) Abstract: We report accurate Ab Initio Hartree Fock (HF) and Density Functional Theory (DFT) studies of the static dipole polarizabilities and first hyperpolarizabilities of the [n] fulvene and the [n,m] fulvalene series of molecules (with n, m = 3,5,7). Calculations are also reported for the parent cycloalkenes: cyclopropene, cyclopentadiene and cycloheptatriene (1-3 respectively). Geometries were optimized at the HF/6-311G(3d,2p) level of theory. All the fulvenes (4-6) and the smaller fulvalenes (7, 9 and 10) are found to be planar. Pentaheptafulvalene (11) is slightly non-planar whilst heptafulvalene (12) has a folded C2h structure. Calculated C-C bond lengths are consistently smaller than the experimental values. Dipole polarizabilities and non-zero hyperpolarizabilities were calculated at the HF/6-311++G(3d,2p) and BLYP/6-311++G(3d,2p) levels of theory, using HF/6-311G(3d,2p) geometries. Dipole polarizabilities correlate well with those given on the basis of atom additivity. Molecules (8), (9) and (11) show very large dipole hyperpolarizabilities.
p. 49-60
Received: 25 May 2000 / Accepted: 23 August 2000 / Published: 9 September 2000
Show/Hide Abstract
| Download PDF Full-text (133 KB) Abstract: TMS is the commonest standard reference for both protons and 13 C NMR spectroscopy. The Magnetic Shielding and its Polarizabilities, plus the static polarizability have been calculated for TMS, tetramethyl ammonium cation and 2,2-dimethylpropane. An investigation of continuum solvation effects on these highly symmetrical molecules, whose first surviving electric moment is the octopole, showed interaction with solvent makes little change to these magnetic properties. This small change is however consistent with both the high symmetry of the molecules and the available extensive experimental data for TMS. A rationalization of the signs and magnitudes of A in a sequence of related molecules has been suggested.
p. 61-62
Received: 7 September 2000 / Published: 30 September 2000
Show/Hide Abstract
| Download PDF Full-text (12 KB) Abstract: n/a
Displaying article 1-4
Plain Text
BibTeX
BibTeX (without abstracts)
Endnote
Endnote (without abstracts)
Tab-delimited
PubMed XML
DOAJ XML
AGRIS XML
to open them.