Density-functional-theory-predicted symmetry lowering from cubic to tetragonal in nickel hexacyanoferrate

Density-functional-theory (DFT) computations on a Prussian blue analogue (PBA), nickel hexacyanoferrate, Ni 2+ 3 [Fe 3+ (CN) 6 ] 2 · n H 2 O, predict the existence of a tetragonal ( P 4 m 2) crystal structure that is energetically degenerate with the previously reported cubic ( F 4 3 m ) structure for this PBA. The proposed tetragonal structure satisfies observations, such as X-ray diffraction and magnetic measurements, that have been reported...