Crystal field theory

About: Crystal field theory is a research topic. Over the lifetime, 1520 publications have been published within this topic receiving 29242 citations. The topic is also known as: CFT.

Multiplet effects in X-ray spectroscopy

Abstract: This review gives an overview of the presence of multiplet effects in X-ray spectroscopy, with an emphasis on X-ray absorption studies on 3d transition metal ions in inorganic oxides and coordination compounds. The first part of the review discusses the basics of multiplet theory and respectively, atomic multiplets, crystal field effects and charge transfer effects are explained. The consequences of 3d-spin–orbit coupling and of 3d systems in symmetries lower than cubic are discussed. The second part of the paper gives a short overview of all X-ray spectroscopies, where the focus is on the multiplet aspects of those spectroscopies and on the various configurations that play a role in combined spectroscopies such as resonant photoemission, resonant X-ray emission and coincidence spectroscopy. The review is concluded with a section that gives an overview of the use of multiplet theory for 3d coordination compounds. Some new developments are sketched, such as the determination of differential orbital covalence and the inclusion of π-(back)bonding.

The CTM4XAS program for EELS and XAS spectral shape analysis of transition metal L edges

Abstract: The CTM4XAS program for the analysis of transition metal L edge Electron Energy Loss Spectroscopy (EELS) or X-ray Absorption Spectra (XAS) is explained. The physical background of the calculations is briefly discussed. The program consists of three theoretical components, based on, respectively, atomic multiplet theory, crystal field theory and charge transfer theory. The theoretical concepts are explained and a number of examples are presented. The calculation of the 2p EELS and XAS spectra of transition metal ions, is given in detail, including their Magnetic Circular Dichroism (MCD). In addition, examples of 1s, 2s, 3s, 2p and 3p X-ray Photoemission Spectroscopy (XPS) are given.

Theory of lanthanide crystal fields

Abstract: Recent progress in understanding the origin of the lanthanide crystal field is summarized. The basic assumption of the crystal field parametrization is shown to be that the crystalline environment can be represented as a one-electron potential, and the consequences of removing this assumption are traced. It is further shown that overlap and covalency make the dominant contributions to the observed field, the electrostatic contributions only being inportant for the potential components with low angular dependence (i.e. the n=2 parameters). In some circumstances it is found that the observed parameters can usefully be analysed into superposed contributions from the neighbouring ions in the crystal. The importance of crystal field concepts in related problems is emphasized as well as the stimulus crystal field theory gives to the development of formalisms for dealing with non-orthogonal basis states.

Optical Spectra of Ni2+, Co2+, and Cu2+ in Tetrahedral Sites in Crystals

Abstract: The polarized absorption spectra of Ni2+ and Co2+ in crystals of ZnO, ZnS, and CdS; Ni2+ in crystals of Cs2ZnCl4 and Cs2ZnBr4; and Cu2+ in ZnO have been measured at 4°K, 77°K, and room temperature. The spectra have been interpreted by the use of crystal field theory for the states of the (3d)n configuration acted on by a potential of predominately Td symmetry. Certain details of the spectra are accounted for by smaller contributions from fields of lower symmetry, notably a C3v potential contribution for the transition metal ions in ZnO. Crystal field, electrostatic repulsion, and spin‐orbit parameters have been obtained for all these cases. An empirical correlation between the electrostatic repulsion parameter, B, for the ions in the crystals and the ligand polarizibility has been obtained. Although the configuration mixing between the states of the configurations (3d)n and (3d)n—1 (4p) has been found to give a negligible contribution to the calculated relative energies of the levels, it does partially ex...

The distribution of transition metal cations in spinels

Abstract: Crystal field theory in conjunction with spectroscopic data may be applied to give quantitatively the d-shell splitting and the resulting stabilization of a transition metal ion in a crystal site of given symmetry. The thermodynamic stabilization values are found for both octahedral and tetrahedral sites in the spinel lattice. The differences between these values is the site preference energy. The cation distributions predicted from this energy are in good agreement with known experimental data. The occurrence of a large Jahn-Teller effect is correlated with tetragonal phase formation.