The activation of MgCl2 is an essential step for preparing performant Ziegler-Natta catalysts (ZNCs), but the structural characterization of the so formed delta-MgCl2 has been left behind due to its complicated disorder. In the current study, synchrotron X-ray total scattering is applied for the structure analysis of delta-MgCl2. Complementary use of powder X-ray diffraction (PXRD) and pair distribution function (PDF) enabled determining the type and extent of disorder for a series of mechanically and chemically activated delta-MgCl2 samples. Moreover, their combination with molecular simulation successfully derived consistent nanoparticle models, where the conventional interpretation of disorderedly stacked nanoplates was justified in a cross-validated manner. (C) 2020 Elsevier Inc. All rights reserved.