Beyond complementarity: a reverse-engineering framework for de novo crystal structure determination from EXAFS

This work introduces reverse EXAFS analysis (REA), a novel, ab initio framework that transforms extended X-ray absorption fine structure (EXAFS) spectroscopy from a complementary local probe into a primary tool for de novo crystal structure determination. By integrating iterative FEFF simulations with a reverse-fitting algorithm, REA directly extracts full crystallographic parameters, lattice constants, space group and atomic positions, from EXAFS oscillations, without requiring the user to supply an initial structural model from X-ray diffraction; instead, candidate models are retrieved from crystallographic databases and evaluated against EXAFS data. Validated on LiCrO₂ and CuFeO₂, REA uncovered unexpected phase complexities in CuFeO₂, identifying secondary CuFe₂O₄ and CuFe₅O₈ phases undetected by conventional methods. This paradigm shift enables accurate structure solving in disordered, nanostructured and novel materials where diffraction fails, establishing EXAFS as a stand-alone crystallographic technique.