Raman studies of phase transitions in Mg(ClO4)2·6H2O crystal

Raman spectra of Mg(ClO4)2·6H2O single crystal in different polarizations in the temperature range 350–110 K are presented. Three phase transitions were found at 325, 272 and 225 K. The transition at 272 K is associated with the rotation of crystallographic a and b axes with respect to the space-fixed coordinate axes X and Y in the ab plane. The transition at 325 K occurs as a result of reorientation of the ClO4− ion and that at 225 K as a result of the tumbling motion of the aquo complex.