Localised dynamics of a dipolar glass (NH4)x K1–x I
Abstract
We report the first inelastic neutron scattering results on the dipolar glass (NH4)x K1 –x I (0.05 < x < 0.70). Three distinct inelastic features are observed at ca. 10, 21 and 31 meV, respectively. These are interpreted in terms of a C3v model for the ammonium ion site. The ammonium ion is shown to lie on its ideal lattice site with its dipole directed along the unique C3v axis. The librational frequencies of the ammonium ion in NH4I (in the NaCl phase) are predicted.