Crystal-field excitations in NiO under high pressure studied by resonant inelastic x-ray scattering
Simo Huotari1, Laura Simonelli, Valentina M Giordano
1Department of Physics, PO Box 64, FI-00014 University of Helsinki, Finland. European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France.
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.
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