Multiplet ligand-field theory (MLFT) or small cluster calculations are useful approaches for calculating X-ray spectroscopy on strongly correlated materials where the spectral lineshape is dominated by strong multiplet effects arising from the Coulomb interactions between the valence electrons and between the valence electrons and the core hole. Since the eigenfunction of a Coulomb multiplet often involves several Slater determinants, they are often poorly described by effective single-particle models, such as density functional theory. For MLFT, one considers a single ion and the effects of the ligands are described by an effective crystal field. This approach often works well when describing X-ray absorption spectroscopy. For X-ray photoemission, screening effects are stronger and the ligands have to be included explicitly. This is generally known as a small-cluster calculation. The spectra are calculated by constructing a many-body Hamiltonian for the system using full configuration-interaction.
|Distribution & Impact
XClaim consists of a Python GUI that interfaces with a precompiled Fortran computation module. Both can be downloaded from the
The package runs on Linux, Windows and MacOS platforms.
This work was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No.DE-FG02-03ER46097, the time-dependent X-ray spectroscopy collaboration as part of the Computational Materials Science Network (CMSCN) under Grants DE-FG02-08ER46540 and DE-SC0007091, and NIU Institute for Nanoscience, Engineering, and Technology. Work at Argonne National Laboratory was supported by the U.S. DOE, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357.
J. Fernández-Rodríguez, B. Toby, and M. van Veenendaal, "Xclaim: a graphical interface for the calculation of core-hole spectroscopies", J. El. Spec. & Rel. Phenom. 202, 81 (2015). doi:10.1016/j.elspec.2015.03.010
J. Fernández-Rodríguez, B. Toby, and M. van Veenendaal, Mixed configuration ground state in Iron(II) Phthalocyanine (m.s. in preparation).