The orientation of NH3D+ in ammonium nickel–sulfate hydrate: A new type of crystalline phase

Abstract
We report the discovery of a new type of phase. The N–D bonds in dilute NH3D+ in the title compound are oriented to a maximum extent at 29 K, but this orientation decreases at both higher and lower temperatures. We attribute the decrease as the temperature is lowered to an increase in the tunneling of the NH3D+ ions.