Obtaining core excitation spectra using ABINIT and NBSE

We present a hybrid approach for GW/Bethe-Salpeter Equation calculations of core excitation spectra including XAS, NRIXS and EELS. The method dubbed OCEAN, is based on 1) {\it ab initio} ground state wavefunctions from the plane-wave pseudopotential code ABINIT; 2) the NIST core-level Bethe-Salpeter Equation Lanczos solver; and 3) a many-pole GW self-energy model (MPSE) to approximate final state broadening and self-energy shifts. An easy to use interface has been developed to drive the different steps required. Extensions to related spectra are briefy discussed. Examples are presented for the F and Li K-edge XAS in LiF, the O K-edge in ice-1h, and others.