Abstract text (incl. figure legends and references)

Scanning diffraction microscopy in the form of ptychography is a powerful method for materials characterization with X-rays and electrons at the nano- and the atomic scale. As radiation sources become brighter and detectors faster, scale-bridging studies and multi-scale phenomena become accessible by this method. However, the current reconstruction algorithms scale poorly to large field of view and thick samples. Here we present an unsupervised reconstruction algorithm inspired by a fast simulation method for scanning transmission electron microscopy (STEM), that offers more than 100x speedup compared to existing 3D phase-reconstruction methods for large fields of view with more than 10^6 diffraction measurements. We demonstrate the approach experimentally in STEM at atomic resolution by sectioning through a highly strained Co3O4 /Mn3O4 core-shell nanoparticle and revealing its 3D structure from a single view.