Preliminary crystal structure of mixed-valency Sr4Ni3O9, the actual formula of the so-called Sr5Ni4O11

Abstract

A crystal structure investigation of the so-called Sr₅Ni₄O₁₁ from single-crystal X-ray data has shown that the composition of this oxide is in fact close to Sr₄Ni₃O₉. The structure has been solved in the trigonal P321 space group. The final refinement gave an R factor of 0.045 for 512 independent reflections. The structure contains NiO₃ chains with two NiO₆ octahedra and one NiO₆ trigonal prism alternating and sharing faces. The chains run along the three-fold axis and are connected by Sr ions. The Ni–O distances seem to indicate a possible repartition of Ni^IV in the octahedral sites and Ni^II in the trigonal prisms.