Raman spectra of a LiN(HxD1-x)4SO4 mixed crystal

Raman spectra of a deuterated lithium ammonium sulphate single crystal are studied at 77 to 493 K. The results show that the I‐II‐III phase transitions are bonded essentially with the dynamics of Li‐SO4 framework; the NH4‐spectra are of a diffusive character so that no clear‐cut conclusions can be drawn about the role of the NH4‐sublattice in these phase transitions. The spectra corroborate the necessity of using several order parameters in the phenomenological description of the phase transitions in this crystal.