Design and discovery of CaKRu₄P₄: a new member of the generalized 1144 structure.

AeAFe₄As₄ (Ae=Ca, Sr; A=K, Rb, Cs) compounds were discovered as a new structural type [1] which has alternate stacking of the Ae and A layers. The AeAFe₄As₄ structure is stabilized by the combination of large Δc (= c^A122-c^Ae122) and small Δa (= a^A122-a^Ae122), where a and c are lattice parameters of the AFe₂As₂ and AeFe₂As₂ parent structures. In this presentation this idea was extended to similar, phosphorus-based 122 compounds with large Δc and small Δa values, in particular CaKRu₄P₄, whose stability was recently predicted by first principle calculations [2]. We synthesize polycrystalline CaKRu₄P₄ by solid state reaction of CaRu₂P₂ and KRu₂P₂. The crystallographic structure and physical properties of CaKRu₄P₄ will be presented.
[1] Akira Iyo, et al., J. Am. Chem. Soc. 138, 3410 (2016)
[2] Song Boqun, et al., APS March Meeting (2019)