Crystallographic features of ammonium fluoro­elpasolites: dynamic orientational disorder in crystals of (NH₄)₃HfF₇ and (NH₄)₃Ti(O₂)F₅

The electron-density profiles of all the constituent atoms in the structures of ammonium fluoroelpasolites enabled the refinement of their real positions. The N2 atom does not escape a special 4b position, but the H2 atoms are disordered in the 96k position instead of 24e and together with the H3 atom in the 32f position they form eight spatial orientations of the ammonium group.