Evidence for weak electronic correlations in Fe pnictides

Using a combination of theoretical techniques we study the XAS and RIXS spectra of three different Fe-pnictide superconductors and parent compounds. Experimental data show that the XAS of the Fe-pnictides is similar to that of Fe metal. Motivated by this fact we analyze the size of electronic correlations, typified by Hubbard's ``U'' and Hund's ``J'', in the Fe-pnictides. Our exact diagonalization cluster calculations include explicit correlations and put an upper limit on U and J. Our relativistic Dirac atomic calculations show the relative unimportance of core-hole multiplet effects and spin-orbit coupling on the spectra. Finally, we present DFT based calculations of the XAS and XES spectra for three Fe-pnictides and Fe metal using the relativistic FEFF8 code and the WIEN2k code.