Crystal fields, local

Several NaCl-type binary compounds, including UN, have been analyzed (14) using both theoretical band structure (itinerant) and crystal field (localized) approaches (although the applicability of one of these approaches generally means that the other is inappropriate). UN may be an intermediate case where neither approach will yield very satisfactory results. Photoemission spectroscopy can yield valuable insights into this problem. 

For lanthanides other than Gd(III), the magnetic anisotropy still depends on the the local coordination environment it determines which crystal field anisotropy terms in Equation 7.2 are allowed by symmetry, the rest simply vanish. However,... 

Reflection contrast Reflection-imaging microscopy Field ion microscopy Quantification in gap between light and em microscopies Useful for imaging highly reflective particles such as silver grains in autoradiographs Atomic structure of crystals Immunoelectron Localization of cellular antigens... 

The above discussion was based on the results of molecular dynamics simulations on unsaturated or conjugated hydrocarbons. Although the general features can be extended to molecular structures of more general types, in practice it is appropriate to consider the specific form of the electron orbitals involved. For instance, d d transitions in transition metal ion complexes involve orbitals mainly localized on the metal ion that, in the crystal field... 

At the beginning of this section we said that a localized picture is very often the best starting point for U, Np and Pu compounds. Is there any clear-cut criterion to direct us in the way of itinerant magnetism Good experimental evidence seems to be - a reduced ordered moment (in particular when it is incompatible with the effective moment in the crystal field scheme ) and - a large electronic specific heat (> 10 mJ/mol K ) and - a reduced magnetic entropy at the transition ( RLn2)... 

These properties of the d-shell chromophore (group) prove the necessity of the localized description of d-electrons of transition metal atom in TMCs with explicit account for effects of electron correlations in it. Incidentally, during the time of QC development (more than three quarters of century) there was a period when two directions based on two different approximate descriptions of electronic structure of molecular systems coexisted. This reproduced division of chemistry itself to organic and inorganic and took into account specificity of the molecules related to these classical fields. The organic QC was then limited by the Hiickel method, the elementary version of the HFR MO LCAO method. The description of inorganic compounds — mainly TMCs,— within the QC of that time was based on the crystal field... 

Localized d or/electrons retain their one-atom manifolds, except that states arising from different d" or f are split by crystal field and spin-orbit coupling. Multiplet splittings due to spin-orbit coupling are larger than crystal-field splittings of Af levels the converse is the case for 3d" levels. The difference in energy between d"(f) and d" (/ 1) manifolds corresponds to the amount of free atom U that is decreased due to interatomic interaction in the solid. 

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