Numerical study of photon spectroscopies for transition-metal oxides and complexes

X-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) have become important techniques for understanding low-energy excitations in transition-metal oxides and electronic transitions transition-metal complexes. A theoretical understanding of these photon spectroscopies for such correlated systems has remained a challenge, especially for understanding momentum dependence and photon-polarization. Here we present the charge transfer full atom multiplet method using exact diagonalization technique for material-specific XAS and RIXS calculations with only minimum adjustable parameters. A few examples such as bulk NiO and molecular Ferrocyanide will be presented and compared with experiments.