Virtual diffraction is a computational technique that enables a synergistic coupling between experiments and atomistic simulations, which can help to elucidate nanoscale structure-property relationships. The research objective herein is to highlight recent advances in the use of virtual diffraction as a method to study the geometry and structure of homophase grain boundaries and heterophase interfaces with direct experimental validation. Virtual selected area diffraction patterns for two types of boundaries-homophase Al twist grain boundaries and heterophase Al2O3/Al interfaces-are created without a priori assumption of the periodic interface structure by computing diffraction intensities across high-resolution, 3-D reciprocal space meshes. In this work, computed diffraction patterns clearly identify Al grain boundary misorientation angles, reveal subsidiary peaks created by the dislocation arrays within select Al grain boundaries, and allow experimental validation of the minimum energy orientation relationship for the Al2O3/Al interface. Due to its advanced implementation, virtual diffraction characterization used throughout this work can be easily extended providing routes for similar analysis and experimental validation of atomistic simulations.