Search results for "Relaxation effect"
showing 4 items of 4 documents
Nuclear magnetic shielding constants in the CC2 model
1997
Abstract Test calculations of nuclear magnetic shielding constants in the CC2 model are performed using the gauge-including atomic orbital approach. Absolute shielding constants are reported for reprsentative first-row hydrides, a few multiply bonded molecules and some challenging cases. The performance of CC2 is analyzed by comparison with experimental data and results from calculations employing more sophisticated treatments of electron correlation. In most cases, CC2 shieldings and chemical shifts are close to those obtained at second-order perturbation theory, despite the fact that the CC2 model includes an approximate treatment of orbital relaxation effects at the correlated level.
Analytical evaluation of first-order electrical properties based on the spin-free Dirac-Coulomb Hamiltonian.
2011
We report an analytical scheme for the calculation of first-order electrical properties using the spin-free Dirac-Coulomb (SFDC) Hamiltonian, thereby exploiting the well-developed density-matrix formulations in nonrelativistic coupled-cluster (CC) derivative theory. Orbital relaxation effects are fully accounted for by including the relaxation of the correlated orbitals with respect to orbitals of all types, viz., frozen-core, occupied, virtual, and negative energy state orbitals. To demonstrate the applicability of the presented scheme, we report benchmark calculations for first-order electrical properties of the hydrogen halides, HX with X = F, Cl, Br, I, At, and a first application to th…
Hybrid materials containing organometallic cations and 3-D anionic metal dicyanamide networks of type [Cp*2M][M′(dca)3]
2004
A new series of hybrid materials of type [Cp*2M][M′(dca)3] has been prepared by cation templation and structurally characterised (M = Fe(III), Co(III); M′ = Mn(II), Fe(II), Co(II), Ni(II), Cd(II); dca− = N(CN)2−). The crystallographic analysis of [Cp*2Fe][Cd(dca)3] showed that the [Cd(dca)3]− anionic framework is of a symmetrical 3-D α-polonium type, containing octahedral Cd nodes and μ1,5-dca bridging ligands. The [Cp*2Fe]+ cations occupy the cube-like cavities within the framework. The cationic and anionic-framework sublattices remain magnetically independent and display susceptibilities, over the range 300 to 2 K, of a Curie–Weiss nature obtained by adding a S = 1/2 (Cp*2Fe+) or a S = 0 …
Correlation of primary relaxations and high-frequency modes in supercooled liquids. I. Theoretical background of a nuclear magnetic resonance experim…
2006
The question regarding a possible correlation of the time scales of primary and secondary relaxations in supercooled liquids is formulated quantitatively. It is shown how this question can be answered using spin-lattice relaxation weighted stimulated-echo experiments, which are presented in an accompanying paper [A. Nowaczyk, B. Geil, G. Hinze, and R. Böhmer, Phys. Rev. E 74, 041505 (2006)]. General theoretical expressions relevant for the description of such experiments in the presence of correlation effects are derived. These expressions are analyzed by Monte Carlo integration for various correlation scenarios also including exchange processes, which are the hallmark of dynamical heteroge…