Interconfigurational fluctuations

Wilson JA (1977) A Generalized Configuration - Dependent Band Model for Lanthanide Compounds and Conditions for Interconfiguration Fluctuations. 32 57-91 Wilson MR (1999) Atomistic Simulations of Liquid Crystals. 94 41-64 Winkler H, see Trautwein AX (1991) 78 1-96... 

Core-level spectra are useful in studying mixed valence (valence instability or interconfigurational fluctuation) in rare-earth systems (e.g. SmS, Ce) which arises when Eexc = n (E -i + FJ 0 where( — , )istheenergydifferencebetweenthe4/ and 4T states and is the energy of the promoted electron. The time scale involved... 

Dependent Band Model for Lanthanide Compounds and Conditions for Interconfiguration Fluctuations J. N Murrell The Potential Energy Surfaces of Polyatomic Molecules J-A-Duffy Optical Electron ativity and Nephelauxetic Effect in Oxide Systems Application to Conducting, Semi-Conducting and Insulating Metal Oxides... 

A Generalized Configuration-Dependent Band Model for Lanthanide Compounds and Conditions for Interconfiguration Fluctuations... 

Many models have been postulated to account for the interconfiguration fluctuations (ICF) in rare earth intermetallic compounds. We will consider Hirst s model which assumes that the 4/ electrons are highly correlated and preserve their atomic-like features during the valence fluctuation. Both the X-ray photoelectron spectra and the magnetic susceptibility of rare earth intermetallic compounds can be successfully explained on the basis of Hirst s model [8,11]. 

According to the model the period r of the interconfigurational fluctuation is given by the width, d ( hr) of the principal band. The average valence V is given by... 

The methods by which the phenomenon of interconfiguration fluctuations may be studied are (i) determination of lattice constant, (ii) magnetic susceptibility measurements, (iii) Mossbauer spectroscopy, (iv) measurement of electrical resistivity, (v) Hall effect, (vi) X-ray absorption spectroscopy and (vii) X-ray photoelectron emission spectroscopy. It is useful to note that a suite of techniques must be used to detect ICF phenomenon in a system. Nuclear magnetic resonance is sparingly used because not all the systems exhibiting ICF contain magnetically active nuclei. 

J.A. Wilson, A generalized configuration-dependent band model for lanthanide compounds and conditions for interconfiguration fluctuations, pp. 58-90, Bell Laboratories, Murray Hill, New Jersey 07974. 

The second chapter deals with quantum chemical considerations, s, p, d and f orbitals, electronic configurations, Pauli s principle, spin-orbit coupling and levels, energy level diagrams, Hund s mles, Racah parameters, oxidation states, HSAB principle, coordination number, lanthanide contraction, interconfiguration fluctuations. This is followed by a chapter dealing with methods of determination of stability constants, stability constants of complexes, thermodynamic consideration, double-double effect, inclined w plot, applications of stability constant data. 

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