Electronic structure of the lanthanides

We will discuss applications of the APS technique to simple as well as multicomponent systems. The results of the applications cited are compared with those from other techniques wherever available. The derivation of the DOS directly from the APS spectrum of 3d transition metals has been dealt with by various authors (Dose et al. 1981). The one-electron theory explains satisfactorily the 3d transition metal spectra, but fails when applied to the lanthanide metals. The electronic structures of the lanthanide metals and their intermetallics as obtained from APS spectra are also discussed. 

Lanthanides Luminescence Applications Lanthanides in Living Systems Lanthanide Oxide/Hydroxide Complexes Lanthanides Coordination Chemistry Sustainability of Rare Earth Resources The Electronic Structure of the Lanthanides Variable Valency. 

Homogeneous Catalysis Lanthanide Halides Organometallic Chemistry Fundamental Properties Tetravalent Chemisiry Inoiganic Tetravalent Chemistry Organometallic The Divalent State in Solid Rare Earth Metal Halides The Electronic Structure of the Lanthanides. 

The lanthanide elements differ from the main group elements and the transition metals because of the nature of the 4f orbitals, which are shielded by the presence of the 5s and 5p electrons (the Xe core). Consequently, 4f electrons possess the interesting characteristic to be inner electrons, i.e., they are closer to the nucleus than the electrons in the 5s and 5p orbitals. This exceptional property fairly screens the 4f electrons from the exterior, so that they are very few affected by the chemical enviromnent. This is the reason why the chemical properties of the series are closely similar, with the exception of the so-called lanthanide contraction (see The Electronic Structure of the Lanthanides). 

Finally, note that lanthanides are naturally occurring in their oxidized form. Their oxidation state is usually 4-3, i.e., it is the most stable one. Therefore, the electronic structure of the lanthanide ions have no electron in the 5d or 6s subshell. In the following sections of this chapter, lanthanides should then be understood as lanthanide ions or lanthanide(ni) unless stated otherwise. 

To understand the surface magnetism of the lanthanides, one needs to understand the electronic structure. The conduction electrons are the medium of exchange interaction between adjacent 4f moments, so that electron itinerancy plays a strong role in lanthanide magnetism. Both the surface magnetic properties and the surface electronic structure of the lanthanide metals differ from that of the bulk. This review will, therefore, often include descriptions of the bulk magnetic and electronic structure so that comparisons between the bulk and the surface can be made more readily. 

As an alternative to the 4f electrons, the 4d and especially 3d core levels, with large cross sections for the excitation with laboratory sources such as AIKa radiation (photon energy 1.486 keV), were very appealing to the experimentalist as possible signals for obtaining, in a fast way, a picture of the underlying electronic structure of the lanthanides. This was especially true for Ce, where - without synchrotron radiation - it was clearly very difficult with X-ray Photoemission Spectroscopy (XPS) to detect the 4f-related intensity (Baer et al. 1978). 

Also reliable thermochemical data for the pure metals have been accumulated, like for example their heats of vaporization (cohesive energy at zero temperature) (Habermann and Daane 1964). Since these measurements all involve energy differences between different states of the lanthanide atoms (ionsX seems possible to interrelate the various data to each other and from this gain further understanding of the electronic structure of the lanthanides. 

In general, the present review describes some fundamental properties of the studied compounds, which, nevertheless, have an independent role for the solution of a number of scientific and applied problems. Accumulated knowledge acquires a fundamental significance due to the fact that the developed system of calculations and evaluations can be used to describe the thermod)mamic properties of unexplored or poorly studied related compounds. It is also promoted by the correlations found between the electronic structure of the lanthanides and the properties established on the molecular and macroscopic levels for the considered compounds. 

Taking into account the perturbing influence of the crystal field potential upon the electronic structure of the lanthanide ion, the wavefunction defined up to the first order in perturbation Vcryst has the following form ... 

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