4f and 5d levels of Ce3+ in D2 eightfold oxygen coordination

TL;DR

This study investigates how the geometry of the first coordination shell around Ce3+ ions in D2 eightfold oxygen sites affects the 4f and 5d energy levels using ab initio methods, revealing specific deformations that cause red shifts.

Contribution

It provides a detailed ab initio analysis of how particular geometric deformations influence the electronic energy levels of Ce3+ in D2 symmetric environments, highlighting the effects of symmetric bond compression and tetragonal bond bending.

Findings

Symmetric Ce-O bond compression shifts the 4f-5d transition to the red.

Tetragonal symmetric bond bending also causes a red shift.

Splittings of 5d and 4f levels are discussed in relation to site geometry.

Abstract

The effects on the 4f and 5d levels of Ce3+ of its first coordination shell geometry in Ce-doped oxides with a D2 8-fold site, like garnets, are studied with embedded cluster, wave function based ab initio methods. The only deformations of a CeO8 cube that are found to shift the lowest 4f-5d transition to the red are the symmetric Ce-O bond compression and the tetragonal symmetric bond bending. These results are analyzed in terms of centroid and ligand field stabilization energy differences. The splittings of the upper 5d levels and of the 4f levels are also discussed.