The temperature dependences of 7Li nuclear magnetic resonance in LiXSO4
(X = K, Rb, Cs, and NH4) single crystals grown by the slow evaporation
method have been investigated by employing a Bruker FT NMR spectrometer. From
the experimental data, the nuclear quadrupole constant, the asymmetry
parameter and the principal axes of the EFG tensor were determined, and the
results were compared with the crystal structure. The temperature dependences
of the quadrupole parameters were explained with a single torsional mode of
the Li-O bond by the Bayer theory. All the LiO4 tetrahedra in four
different crystals showed torsional motion about the X-axis of the EFG
tensor. Based on these results, the differences in atomic weight of X in the
LiXSO4 single crystals are responsible for the differences in the torsional
angular frequencies.