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Raman and i.r. spectra of zinc, cadmium and calcium nitrate: A study of the low temperature phase transitions in calcium nitrate

1976; Pergamon Press; Volume: 32; Issue: 2 Linguagem: Inglês

10.1016/0584-8539(76)80090-6

1873-3824

M. H. Brooker,

Crystal structures of chemical compounds

Raman and i.r. spectra have been obtained for anhydrous Ca(NO3)2 at 298, 273, 195 and 77 K and for Cd(NO3)2 and Zn(NO3)2 at 298 and 77 K. The vibrational spectrum of Ca(NO3)2 at room temperature is in excellent agreement with a factor group analysis based on the Th6 space group. Below room temperature, new bands appear which indicate that Ca(NO3)2 undergoes two phase changes between 77 and 298 K (Phase III Phase II Phase I). Anhydrous Cd(NO3)2 and Zn(NO3)2 do not appear to undergo phase changes between 77 and 298 K. The Raman spectra of Ca(NO3)2 (III), Ca(NO3)2 (II), Cd(NO3)2 (II) and Zn(NO3)2 suggest the presence of crystallographically non-equivalent sets of nitrate groups. Assignments have been aided by the use of 18O enriched nitrates.