Electronic properties of lanthanides

8 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. 

In actinides, the J terms are closer in eneigy and more heavily admixed by spin-orbit coupling. 

Ligand field effects split the J manifold in a way that is not easily predicted without specific calculations. However, the overall splitting is such that many of the levels are appreciably populated at room temperature. An elegant procedure that takes such effects into account in a general way with respect to pseudocontact shifts of metal-centered origin has been provided by Bleaney [79]. 

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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. 

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... 

Di Bari L, Pintacuda G, Salvador P, Dickins RS, Parker D. Effect of Axial Ligation on the Magnetic and Electronic Properties of Lanthanide Complexes of Octadentate Ligands. J Am Chem Soc 2000 122 9257-9264. 

The determination of the electronic structure of lanthanide-doped materials and the prediction of the optical properties are not trivial tasks. The standard ligand field models lack predictive power and undergoes parametric uncertainty at low symmetry, while customary computation methods, such as DFT, cannot be used in a routine manner for ligand field on lanthanide accounts. The ligand field density functional theory (LFDFT) algorithm23-30 consists of a customized conduct of nonempirical DFT calculations, extracting reliable parameters that can be used in further numeric experiments, relevant for the prediction in luminescent materials science.31 These series of parameters, which have to be determined in order to analyze the problem of two-open-shell 4f and 5d electrons in lanthanide materials, are as follows. 

Electronic Structure and Magnetic Properties of Lanthanide Molecular Complexes... 

In spite of considerable similarities between the chemical properties of lanthanides and actinides, the trivalent oxidation state is not stable for the early members of the actinide series. Due to larger ionic radii and the presence of shielding electrons, the 5f electrons of actinides are subjected to a weaker attraction from the nuclear charge than the corresponding 4f electrons of lanthanides. The greater stability of tetrapositive ions of actinides such as Th and Pu is attributed to the smaller values of fourth ionization potential for 5f electrons compared to 4f electrons of lanthanides, an effect that has been observed in aqueous solution of Th and Ce (2). Thus, thorium... 

In the above sections, our attention was primarily focused on the structural and optical properties of lanthanide doped in nanoparticles such as spherical QDs. Lanthanides doped in some other novel low-dimensional nanostructures including core-shell, one-dimensional (ID) nanowires and nanotubes, two-dimensional (2D) nanofilms, hollow nanospheres, 2D nanosheets and nanodisks have also attracted extensive attention. It is expected that their unique structures could result in unusual mechanical, electronic, optical and magnetic properties. So far few papers have been reported for lanthanide ions other than Eu3+ in these materials. Much attention is focused on the optical properties of Eu3+ ions in view of their very good spectroscopic properties. 

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