Lanthanides electronic properties

The wave functions of the ground and excited states of lanthanides have a truly multiconfigurational character.1 Therefore, computational description of both the ground state and the low-lying excited states, which are important for magnetic behaviour, is only possible by a multiconfigurational ab initio method. In this respect, the C ASSCF method proved to be a reliable tool for the description of electronic properties of lanthanide complexes. 

In Part II. Figs. 8 and 11 showed that in Icinthanides the 4f electrons can be described as localized so to be treated, in all respects, as atomic electrons. Thus, for instance, in the lanthanide metcds, properties related to the conduction band (which has essentially a (5d, 6 s) character) may be - in first approximation - separated from the magnetic properties related to the highly localized 4f electrons. 

THE CASE OF LANTHANIDES AND ACTINIDES 2.8.1 Electronic properties of lanthanides... 

The electronic properties of lanthanides are peculiar, in that spin-orbit interactions are very large, laiger in fact than ligand field effects. Therefore, a somewhat different formalism is used. 

Lanthanides are coextracted with actinides and then separated from actinides, which are forecasted to be sent to a repository. The lanthanide elements comprise a unique series of metals in the periodic table. These metals are distinctive in terms of size, valence orbitals, electrophilicity, and magnetic and electronic properties, such that some members of the series are currently the best metals for certain applications. Increased use of the lanthanides in the future is likely, because their unusual combination of physical properties can be exploited to accomplish new types of chemical transformations. These elements coextracted with actinides and then separated from the latter, could in the future be recovered and used (among the lanthanides, only 151Sm is a long-lived isotope (half-life 90 years)).4... 

Lanthanides activated luminescent materials are widely used for solid-state lasers, luminescent lamps, flat displays, optical fiber communication systems, and other photonic devices. It is because of the unique solid-state electronic properties that enable lanthanide ions in solids to emit photons efficiently in visible and near IR region. Due to the pioneer work by Dieke, Judd, Wyboume, and others in theoretical and experimental studies of the... 

Lanthanide(III) Pc doubledecker complexes, LnPc2, possess peculiar electronic properties which make them the first molecular semiconductors [287]. Applications in the field of high speed thin film electronics have been discussed (by Simon et al.). Like the silylamides, they are also sublimable. The radical... 

Lanthanide metallofullerenes are novel forms of fullerene-related materials which were first obtained in their purified form in January 1993 (Shinohara et al., 1993a). Since then, as detailed in this paper, numerous investigations into various aspects of metallofullerenes have been intensively carried out by various research groups. These studies have revealed unique structural and novel electronic properties of the metallofullerenes. 

Figure 5.3 The structure of [La(al-P2Wn06i)2] [13]. (Reprinted with permission from L. Fiesel-mann, et al., Influence of steric and electronic properties of the defect site, lanthanide ionic radii, and solution conditions on the composition of lanthanide(III) al-P2Wi70gj polyoxometalates, Inorganic Chemistry, 44, no. 10, 3569-3578 (Figure 2), 2005. 2005 American Chemical Society.)...

This phenomena originates from the intrinsic electron properties of lanthanide ions, and can be modulated by the surrounding ligand field and symmetry of the compound. There is no... 

Oxides of the lanthanide rare earth elements share some of the properties of transition-metal oxides, at least for cations that can have two stable valence states. (None of the lanthanide rare earth cations have more than two ionic valence states.) Oxides of those elements that can only have a single ionic valence are subject to the limitations imposed on similar non-transition-metal oxides. One actinide rare-earth oxide, UO2, has understandably received quite a bit of attention from surface scientists [1]. Since U can exist in four non-zero valence states, UO2 behaves more like the transition-metal oxides. The electronic properties of rare-earth oxides differ from those of transition-metal oxides, however, because of the presence of partially filled f-electron shells, where the f-electrons are spatially more highly localized than are d-electrons. 

Recent progress in the chemistry of structurally well-defined lanthanide ketyl and ketone dianion complexes is reviewed, with particular emphasis on the ligand effects on the reactivity of these complexes. It has been demonstrated that the stability and reactivity of the ketyl radical and ketone dianion species strongly depend on the steric and electronic properties of the ancillary ligands, the structure of their parent ketones, as well as the nature of the metals to which they are bound. Fine-tuning these factors can control the reactivity of these species. Generation and reactions of dianionic thioketone and imine species are also briefly described. 

Another example of this kind of transition is shown in table 11.1, taken from the work of Smith and Kmetko [601]. It is a quasiperiodic table of all the transition elements and lanthanides in the periodic table, arranged in order of mean localised radius in the vertical direction, and adjusted horizontally so that filled and empty d and / subshells coincide. What Smith and Kmetko discovered is that a broad diagonal sweep across this table separates metals with localised electron properties (magnets) from those with itinerant electron properties (conductors). This boundary (shown as a shaded curve in the figure) is the locus of the Mott transition. Metals lying along this curve are sensitive to pressure effects (Ce has an isomorphic phase transition from the a to the 7 phase at about 1 kbar, U becomes... 

It is generally accepted nowadays that the sequentially increasing occupation of 5f states dominates the electronic properties in the series of actinide elements (see table 2.1). The analogy with lanthanides, in which the 4f states are gradually filled, is not complete. The 4f electronic states are confined deeply in the core of the lanthanide ion and can be treated in most cases as localized. On the other hand, a non-negligi-ble overlap of the more extended 5f wave functions belonging to neighbouring actinide atoms in a solid leads to the delocalization of the 5f states which resembles the formation of the d band in transition metals. The question about the localized versus itinerant 5f electron behaviour has become one of the most central ones within electronic structure considerations. This controversial behaviour is quite well... 

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