High-order multiple-scattering calculations of x-ray-absorption fine structure

High-order scattering is found to be essential for the convergence of the multiple-scattering (MS) theory of x-ray-absorption fine structure, both in the near-edge and the extended regimes. These contributions are calculated using an ab initio curved-wave scattering-matrix formalism. Convergence to full MS accuracy is demonstrated for fcc Cu, as well as for molecular ${\mathrm{O}}_2$ and ${\mathrm{N}}_2$, where our approach provides a high-order MS interpretation of the ${\mathrm{\sigma }}^{\mathrm{*}}$ shape resonances.