  NiO6-octahedral tilts in ultrathin LaNiO3 films were studied using position
averaged convergent beam electron diffraction (PACBED) in scanning transmission
electron microscopy. Both the type and magnitude of the octahedral tilts were
determined by comparing PACBED experiments to frozen phonon multislice
simulations. It is shown that the out-of-plane octahedral tilt of an epitaxial
film under biaxial tensile stress (0.78 % in-plane tensile strain) increases by
~ 20%, while the in-plane rotation decreases by ~ 80%, compared to the
unstrained bulk material.
