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Comparative Electronic Structure of a Lanthanide and Actinide Diatomic Oxide: Nd versus U

Published

Author(s)

Morris Krauss, W J. Stevens

Abstract

Using a modified version of the ALCHEMY electronic structure code and relativistic pseudopotentials, the electronic structure of the ground and low-lying excited states of UO, NdO, and NdO+ have been calculated at the Hartree-Fock (HF) and multiconfiguration self-consistent-field (MCSCF) levels of theory. Including results from an earlier study of UO+ this provides the information for a comparative analysis of a lanthanide and an actinide diatomic oxide. UO and NdO are both described formally as M+2O-2 and the cations as M+3O-2, but the HF and MCSCF calculations show that these systems are considerably less ionic due to large charge back-transfer in the p orbitals. The electronic states putatively arise from the ligand field (oxygen anion) perturbed f4, sf3, df3, sdf2, or s2f2 states of M+2 and f3, sf2 or df2 states of M+3. Molecular orbital results show a substantial stabilization of the sf3 or s2f2 configurations relative to the f4 or df3 configurations that are the even or odd parity ground states in the M+2 free ion. The compact f and d orbitals are more destabilized by the anion field than the diffuse s orbital. The ground states of the neutral species are dominated by orbitals arising from the M+2 sf3 term, and all the potential energy curves arising from this configuration are similar, which allows an estimate of the vibrational frequencies for UO and NdO of 862 cm-1 and 836 cm-1, respectively. For NdO+ and UO+ the excitation energies for the W states were calculated with a valence configuration interaction method using ab initio effective spin-orbit operators to couple the molecular orbital configurations. The results for NdO+ are very comparable with the results for UO+, and show the vibrational and electronic states to be interleaved.
Citation
Molecular Physics
Volume
101
Issue
1-2

Keywords

cation oxides, Hartree-Fock, neodymium oxide, spectroscopic constants, uranium oxide, valence configuration interaction

Citation

Krauss, M. and Stevens, W. (2003), Comparative Electronic Structure of a Lanthanide and Actinide Diatomic Oxide: Nd versus U, Molecular Physics (Accessed April 15, 2024)
Created January 1, 2003, Updated February 19, 2017