Stacking Versatility in Alkali-Mixed Honeycomb Layered NaKNi₂TeO₆

The reaction between P2-type honeycomb layered oxides Na₂Ni₂TeO₆ and K₂Ni₂TeO₆ enables the formation of NaKNi₂TeO₆. The compound is characterized by X-ray diffraction and ²³Na solid-state nuclear magnetic resonance spectroscopy, and the structure is discussed through density functional theory calculations. In addition to the honeycomb Ni/Te cationic ordering, NaKNi₂TeO₆ exhibits a unique example of alternation of sodium and potassium layers instead of a random alkali-mixed occupancy. Stacking fault simulations underline the impact of the successive position of the Ni/Te honeycomb layers and validate the presence of multiple stacking sequences within the powder material, in proportions that evolve with the synthesis conditions. In a broader context, this work contributes to a better understanding of the alkali-mixed layered compounds.