Lithium hydroxide monohydrate single crystals: infrared reflectivity and Raman study

Large (centimetre size) single crystals of lithium hydroxide monohydrate, LiOH·H2O, were grown by slow evaporation of an aqueous solution at ambient temperature. Infrared reflectivity and Raman spectra of the single crystals were observed for the first time and studied experimentally at room temperature. The former spectrum measured over the 400– 4000 cm−1 range contains several bands in the 400– 800 cm−1 region only. The Raman spectrum obtained by argon ion laser irradiation exhibits a single peak of the internal mode of the hydroxyls and nine distinct peaks in the 60– 900 cm−1 region. The assumption that the water molecules behave as structural units consisting of the H+ and OH− ions allowed tentative assignments of the nine Raman peaks to the lattice modes corresponding to movements of the H+ and the hydroxyl and also the Li+ and the hydroxyl against each other.