Spin properties models

Transitions from a localized to an itinerant state of an unfilled shell are not a special property of actinides they can, for instance, be induced by pressure as they rue in Ce and in other lanthanides or heavy actinides under pressure (see Chap. C). The uniqueness for the actinide metals series lies in the fact that the transition occurs naturally almost as a pure consequence of the increase of the magnetic moment due to unpaired spins, which is maximum at the half-filled shell. The concept has resulted in re-writing the Periodic Chart in such a way as to make the onset of an atomic magnetic moment the ordering rule (see Fig. 1 of Chap. E). Whether the spin-polarisation model is the only way to explain the transition remains an open question. In a very recent article by Harrison an Ander-... 

In the preceding section we presented the experimental evidence in support of the spin-coupled model proposed by Gibson et al. (148) and Thornley et at. (150) for the plant-type ferredoxins. However, the spin-coupled model does not provide a spatial or configurational model for the active center. Therefore we proceed to a more detailed analysis with the goal of asserting a proper chemical and structural model of the active center. The following properties of the active site of these proteins are well-substantiated experimentally. 

Calculations are presented and data are reviewed on the properties of the high-j states in the light Au nuclei. Both prolate and oblate structures are observed in this region. It is found that the collective model describes well the band- head and the high-spin properties of the h9/2 and ii3/2 proton states, without resort to an "intruder state" phenomenology. 

The radical site prior to the initiating proton transfer is, moreover, proposed to be located at the axial tyrosine (Tyr495), rather than at the equatorial thioether substituted Tyr272, as previously suggested. This would bring consistence between GO and model experiments by Stack, where there are strong indications that the radical resides axially. The cysteine cross-link, finally, was shown to have a very small effect on energetics and spin properties of the system. 

Electronic and spin properties of NV-centers in such nanostructured samples are not yet studied. The first theoretical results obtained with the use of quantum chemical methods are reported below. For modeling of the NV- center in diamond nanostructures, the CxHy[NV] clusters were used. In this paper we study the influence of the surface of nano-diamonds containing NV-centers on their structural and spin properties. 

The Blume-Emery-Griffiths (BEG) model is one of the well-known spin lattice models in equilibrium statistical mechanics. It was originally introduced with the aim to account for phase separation in helium mixtures [30]. Besides various thermodynamic properties, the model has been extended to study the structural phase transitions in many bulk systems. By... 

Yalgrn O, Erdem R, Demir Z. Magnetic properties and size effects of spin-1/2 and spin-1 models of core-surface nanoparticles in different type lattices. In Abbass Ha-shim, editor. Smart Nanoparticles Technology InTech 2012. p. 541-560. DOI 10.5772/34706. 

Spin properties are notoriously difficult to calculate accurately57. Here, we are actually calculating spin populations, with their intrinsic uncertainties, and not the directly observed hyperfine interactions. On the other hand, analyses of the hyperfine interactions in the ESR spectra to give experimental atomic orbital occupancies for the radical electron are based on a simplistic, rigid linear combination of atomic orbitals (LCAO)-MO model with the reference electron-nuclear coupling parameters taken from the free atom. No allowance is made for radial or angular polarization of the atomic orbitals in the molecular environment. Thus agreement at these levels between calculated and experimental values can only be qualitative, at best. 

SPIN PROPERTIES OF NANODIAMONDS WITH A SINGLE [NV] CENTER BY AB INITIO MODELING... 

DFT MODELING OF STRUCTURAL, ELECTRONIC AND SPIN PROPERTIES OF NICKEL-NITROGEN-CONTAINING (NE8) CENTER IN NANODIAMOND... 

The detailed proof of this conceptual model is difficult experimentally, although it is generally supported by the existing experimental data and melt spinning process model. The overall veracity of the model is less important than the utility of the model in predicting process-structure-property relationships. Important implications of the model are as follows ... 

The synthesis and characterization of poly(hexamethylene sebacate-tiimethyl-siloxane) block copolymers, prepared by coupling Cl- or McjNH-terminated dimethylsiloxanes with OH-terminated poly(hexamethylene sebacate), have been studied. The copolymers containing 19—90% siloxane were characterized by n.m.r., viscosity, DSC and CPC. All the polymers were found to be crystalline. The copolymers containing <69% siloxane, when cast from solution or melts, indicated a reduction in spherulite size as the siloxane concentration increased, although only a small m.pt. depression was observed. All the copolymers have critical surface tensions similar to dimethylsiloxane homopolymers. Polycarbonate-Siloxane Copolymers.—A model has been proposed to predict the micromorphology and mechanical properties of block copolymers of bisphenol-A polycarbonate and poly(dimethylsiloxane). N.m.r. data upon 65 35 (wt%) copolymer of poly(dimethylsiloxane) and bisphenol-A polycarbonate, with block lengths of 20—100 monomer units, were found to be in agreement with the predictions of a spin-diffusion model. ... 

Even though molecular mechanics and semiempirical methods are capable of describing a great many molecular properties, and more are being added every year, certain properties are beyond the scope of either approach. In such cases ab initio methods may offer the only theoretical model capable of attacking the problem. For example, neither method can accurately treat the manifold of valence and Rydberg excited states of linear polyenes. Nor can they handle the hyperfine spin properties of first- or second-row elements. 

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