Cation Coordination Preferences toward Stacking Design in Layered Perovskites along the Perovskite [111] Direction.

Crystal structures, particularly those of oxides, are viewed as architectures composed of coordination polyhedra, such as tetrahedra, octahedra, and cuboctahedra. While this perspective has long enabled electronic tuning via elemental substitution within known frameworks, its application to the design of new crystal structures remains limited. In this study, we explore cation coordination preferences as a design guideline for understanding and biasing the stacking periodicity of oxygen-deficient [111]p-layered perovskites (p denotes a primitive cubic perovskite cell), which consist of sequential tetrahedral and octahedral layers. We statistically analyzed coordination environments across a crystallographic database, identifying each cation's coordination preference. By selecting appropriate cations with strong tetrahedral or octahedral coordination preferences, we successfully obtained two independent series of [111]p-layered perovskite compounds using different approaches: (i) elemental ratio tuning in the Ba-Sc-Ti-Ge-O system and (ii) valence-state control via nitridation in the Sr-V-O-N system. The appropriate ratio of tetrahedral- and octahedral-preferring cations enables tuning of stacking tendencies. Additional parameters, such as cation size and external pressure, further influence the detailed local structures, as revealed by theoretical calculations. These results highlight the role of local coordination preference to rationally design infinite crystal architectures.