Paper AS-MoM8
XPS Spectra and Bonding In Ionic Transition Metal Compounds

Monday, October 22, 2018, 10:40 am, Room 204

In previous work, [1-3] it has been shown that the cation 2p XPS can reflect the extent of the covalent bonding between the metal cation and the ligands in formally fully ionic TM compounds (ie a nominal "oxidation state"). In the present work, the dependence of the 3p XPS on the covalent character and the charge state of the cation is compared to 2p for selected oxides and halides. The objective is to determine the extent to which the 3p XPS can be used to identify the open shell occupation of the cation; i.e., the nominal oxidation state. It is also of concern to show how the covalent character of the compound modifies the 3p XPS from that for an ideal, isolated, atomic cation. The systems that have been examined include Mn and Fe oxides and halides which are compared with experiment, with each other, and with the calculated XPS of isolated Mn and Fe cations. For the theoretical results, ab initio wavefunctions, WF, have been determined and have been used to obtain the energies and intensities of the cation 2p and 3p XPS. The compounds are modelled with embedded clusters [4 ] and the WFs are solutions of the Dirac-Coulomb Hamiltonian. Implications for the limitations of quantitation, both elemental and chemical compound, using XPS peak intensities together with standards or theoretical cross-sections, are also discussed

1. C. J. Nelin, P. S. Bagus, C. R. Brundle, E. S. Ilton, and K. M. Rosso, J. Chem. Phys. (to be submitted).

2. P. Bagus, C. R. Brundle, and C. J. Nelin, J. Chem. Phys. (to be submitted).

3. P.Bagus, C. R. Brundle, and C. J. Nelin, presented at the AVS International Symposium, 2017

4. P. S. Bagus, E. S. Ilton, and C. J. Nelin, Surf. Sci. Rep. , 273 (2013).