Order-disorder phase transition in the first thiocyanate-bridged double perovskite-type coordination polymer: [NH4](2)[NiCd(SCN)(6)]

The first thiocyanate-bridged double perovskite-type coordination polymer [NH4](2)[NiCd(SCN)(6)] is reported here, which undergoes a reversible structural phase transition at around 120 K. An order-disorder mechanism for this transition is disclosed by X-ray structural analyses, dielectric measurement, as well as molecular dynamics simulations.