Discovering planar disorder in close-packed structures from x-ray diffraction: Beyond the fault model

We solve a long-standing problem---determining structural information for disordered materials from their diffraction spectra---for the special case of planar disorder in close-packed structures (CPS's). Our solution offers the most complete possible statistical description of the disorder and, from it, we find the minimum effective memory length for stacking sequences in CPS's. We contrast this description with the so-called ``fault'' model by comparing the structures inferred using both approaches on two previously published zinc sulphide diffraction spectra.