Structure and dynamics of ammonia in Li-ammonia intercalated TiS₂: a proton NMR study

Measurements of NMR line widths and spin-lattice relaxation times for protons, as functions of temperature and NMR frequency, have in recent years yielded much information about the ammonia molecule intercalated into TiS₂. In conjunction with neutron powder diffraction studies, NMR has been used to probe: (1) intercalated ammonia's molecular motions, (2) distortions in its structure and (3) bonding interactions with its host. The effects of intercalation with Li-ammonia solutions, instead of pure NH₃, have been found to be especially large on the first and third of these, indicating a restricted range for rotational motion of the molecule during diffusion and at the same time weakened bonding of the ammonia protons to TiS₂ sulfur layers. Frequency and temperature dependences of spectral density functions (from T₁ measurements) have been examined for evidence of two-dimensional diffusion. Current findings from NMR bearing on these and related subjects will be reviewed, and comparisons with NH₃-intercalated TiS₂ will be made.