Coupled Compositional and Displacive Modulations in KLaMnWO Revealed by Atomic Resolution Imaging.

Complex compositional and displacive modulations of the crystal structure of KLaMnWO are imaged with atomic resolution by means of scanning transmission electron microscopy (STEM). This oxide is stabilized by cation vacancies leading to a LaKMnWO stoichiometry. Compositional modulation on both the K and La layers are revealed in the high-angle annular dark-field STEM (HAADF-STEM) images. The compositional modulation within the La layer is coupled with the modulation of the octahedral tilting, which is exposed by imaging of the anion sublattice in annular bright-field STEM (ABF-STEM) images. These complex modulations are accommodated in a 5√2 × 5√2 × 2 perovskite-type structure.