11 research outputs found
Intra- site 4f-5d electronic correlations in the quadrupolar model of the gamma-alpha phase transition in Ce
As a possible mechanism of the phase transition in pristine
cerium a change of the electronic density from a disordered state with symmetry
Fm-3m to an ordered state Pa-3 has been proposed. Here we include on-site and
inter- site electron correlations involving one localized 4f-electron and one
conduction 5d-electron per atom. The model is used to calculate the crystal
field of -Ce and the temperature evolution of the mean-field of
-Ce. The formalism can be applied to crystals where quadrupolar
ordering involves several electrons on the same site.Comment: 12 pages, 2 figures, 4 tables, submitted to Phys. Rev.
CORRELATIONS BETWEEN ELECTRONIC STRUCTURE, THERMODYNAMICS AND CRYSTAL STRUCTUREAbout the correlation between electronic configurations of actinide ions and the properties of their compounds
L'objet principal de cet article est de montrer l'importance des énergies de reconstruction sur les propriétés des actinides tant à l'état solide qu'en solution. En raison du dualisme spécifique de localisation-délocalisation des électrons 5f et 6d, des ondes de densité de charge peuvent se produire dans les composés cristallins à basse température. Dans un modèle de Hubbard étendu à deux bandes et prenant en compte les interactions de Coulomb intra- et inter-sites ainsi que l'énergie cinétique, on obtient les critères d'apparition des ondes de charge et d'orbitales. L'ordre orbital peut s'accompagner de la formation d'onde de densité de spin. Quelques considérations sont présentées sur la supraconductivité pour laquelle on suggère que la formation de paires d'électrons dans un état de valence intermédiaire est l'un des mécanismes importants. Le rôle de l'énergie d'excitation sur la stabilité et la géométrie des groupes actinyls est analysé. Une estimation des potentiels d'oxydation pour Cm(IV-V), Cm(V-VI) et Cm(VI-VII) est donnée. On montre que, pour les cations AnO+2, il est possible d'avoir une distorsion de la structure linéaire vers une structure courbée.The main purpose of this paper is to show the importance of the reconstruction energies on the actinide properties both in solid state and solutions. As a consequence of the specific dualism localization-delocalization of the 5f and 6d electrons, charge waves can occur in crystal compounds at low temperature. In an extended two-band Hubbard model which takes into account the intra- and inter-site Coulomb interactions as well as the kinetic energy, the criteria for the occurrence of the charge and orbital waves are obtained. Orbital ordering can be accompanied by spin density wave formation. Partial attention is given to the occurrence of supraconductivity, it is proposed that electron pair formation in a mixed valence state is one of the important mechanisms of supraconductivity state formation. The influence of the excitation energy on the stability and geometry is analysed. Estimates of the Cm(IV-V), Cm(V-VI) and Cm(VI-VII) oxidation potentials are given. It is shown that distortion from the linear to the bent structure is possible for AnO+2 cations
Nanochemistry and supramolecular chemistry of actinides and lanthanides: Problems and prospects
Redox reactions for group 5 elements, including element 105, in aqueous solutions
SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman
Relativistic effects in physics and chemistry of element 105. Pt. 2 Electronic structure and properties of group 5 elements bromides
SIGLEAvailable from TIB Hannover: RO 801(92-03) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman