Xclaim (x-ray core level atomic multiplets) is a graphical interface for the calculation of core-hole spectroscopy and ground state properties within a charge-transfer multiplet model taking into account a many-body hamiltonian with Coulomb, spin-orb
it, crystal-field, and hybridization interactions. Using Hartree-Fock estimates for the Coulomb and spin-orbit interactions and ligand field parameters (crystal-field, hybridization and charge-transfer energy) the program can calculate x-ray absorption spectroscopy (XAS), x-ray photoemission spectroscopy (XPS), photoemission spectrospcy (PES) and inverse photoemission (IPES) for d- and f-valence metals and different absorption edges. The program runs in Linux, Windows and MacOS platforms.
We calculate the angular dependence of the x-ray linear and circular dichroism at the $L_{2,3}$ edges of $alpha$-Fe(II) Phthalocyanine (FePc) thin films using a ligand field model with full configuration interaction. We find the best agreement with t
he experimental spectra for a mixed ground state of $^3E_{g}(a_{1g}^2e_g^3b_{2g}^1)$ and $^3B_{2g}(a_{1g}^1e_g^4b_{2g}^1)$ with the two configurations coupled by the spin-orbit interaction. The $^3E_{g}(b)$ and $^3B_{2g}$ states have an easy axis and plane anisotropies, respectively. Our model accounts for an easy-plane magnetic anisotropy and the measured magnitudes of the in-plane orbital and spin moments. The proximity in energy of the two configurations allows a switching of the magnetic anisotropy from easy plane to easy axis with a small change in the crystal field, as recently observed for FePc adsorbed on an oxidized Cu surface. We also discuss the possibility of a quintet ground state ($^5A_{1g}$ is 250~meV above the ground state) with planar anisotropy by manipulation of the Fe-C bond length by depositing the complex on a substrate that is subjected to a mechanical strain.
The dependence with energy of the resonant soft x-ray Bragg diffraction intensity in DyB$_2$C$_2$ for the $(00{1/2})$ reflection at the Dy M$_{4,5}$ edges have been calculated by using an atomic multiplet hamiltonian including the effect of crystal f
ield and introducing an intra-atomic quadrupolar interaction between the 3d core and 4f valence shell. These calculations are compared with the experimental results (Mulders et al., J. Phys.: Condens. Matter 18 (2006) 11195) in the antiferroquadrupolar and antiferromagnetic phases of DyB$_2$C$_2$. We reproduce all the features appearing $(00{1/2})$ reflection energy profile in the antiferroquadrupolar ordered phase, and we reproduce the behaviour of the resonant x-ray scattering intensity at different energies in the vicinity of the Dy M$_5$ edge when the temperature is lowered within the antiferromagnetic phase.
