Prediction of a New Layered Polymorph of FeS 2 with Fe 3+ S 2- (S 2 2- ) 1/2 Structure.

The never-elucidated crystal structure of metastable iron disulfide FeS2 resulting from the full deintercalation of Li in Li2FeS2 has been cracked thanks to crystal structure prediction searches based on an evolutionary algorithm combined with first-principles calculations accounting for experimental observations. Besides the newly layered C2/m polymorph of iron disulfide, two-dimensional dynamically stable FeS2 phases are proposed that contain sulfides and/or persulfide S(2)( )motifs.