title: Crystal-field excitations in NiO under high pressure studied by resonant inelastic x-ray scattering.
abstract: We report a study on charge-neutral crystal-field (dd) excitations in NiO as a function of applied pressure up to 55 GPa, using resonant inelastic x-ray scattering spectroscopy at the Ni K edge. We find distinct signatures of the pressure-induced modifications to the 3d orbital energies as a function of pressure. These modifications are experimentally evidenced by a subtle splitting of the dd-excitation resonance energies. We compare the experimental results to a charge-transfer cluster-model calculation, and a LSDA + U calculation of the ground state as a function of lattice constant. We thus show how resonant inelastic x-ray scattering spectroscopy is able to give insights into the manifold of excited states even in conditions that are difficult to access with many traditional experimental techniques.
authors.affiliation: Department of Physics, PO Box 64, FI-00014 University of Helsinki, Finland. European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France.
authors.forename: Simo
authors.initials: S
authors.lastname: Huotari
authors.forename: Laura
authors.initials: L
authors.lastname: Simonelli
authors.forename: Valentina M
authors.initials: VM
authors.lastname: Giordano
authors.forename: Anna E
authors.initials: AE
authors.lastname: Rintala
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Sahle
authors.forename: Mikko
authors.initials: M
authors.lastname: Hakala
authors.forename: Pieter
authors.initials: P
authors.lastname: Glatzel
authors.forename: Roberto
authors.initials: R
authors.lastname: Verbeni
authors.forename: Giulio
authors.initials: G
authors.lastname: Monaco