  Recently a highly ordered Moir\'e dislocation lattice was identified at the
interface between a \ce{SrTiO3} (STO) thin film and the
(LaAlO$_3$)$_{0.3}$(Sr$_2$TaAlO$_6$)$_{0.7}$ (LSAT) substrate. A fundamental
understanding of the local ionic and electronic structure around the
dislocation cores is crucial to further engineer the properties of these
complex multifunctional heterostructures. Here we combine experimental
characterization via analytical scanning transmission electron microscopy with
results of molecular dynamics and density functional theory calculations to
gain insights into the structure and defect chemistry of these dislocation
arrays. Our results show that these dislocations lead to undercoordinated Ta/Al
cations at the dislocation core, where oxygen vacancies can easily be formed,
further facilitated by the presence of cation vacancies. The reduced Ti$^{3+}$
observed experimentally at the dislocations by electron energy-loss
spectroscopy are a consequence of both the structure of the dislocation itself,
as well as of the electron-doping due to oxygen vacancy formation. Finally, the
experimentally observed Ti diffusion into LSAT around the dislocation core
occurs only together with cation-vacancy formation in LSAT or Ta diffusion into
STO.
