The Raman spectrum of copper formate tetrahydrate

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Abstract
The Raman spectrum of copper formate tetrahydrate Cu(COOH)2.4H2O, has been determined in the range 3500 to 79 cm-1 from 90 to 250 K. Several lines are found to disappear rather abruptly as the antiferroelectric transition temperature 235.5 K is crossed. By comparison with the spectrum of the deuterate, Cu(COOH)2.4D2O, at 90 K, some of these lines are identified as translatory and rotatory water modes. This agrees with crystallographic and other evidence that ordering of the water molecules occurs at the phase transition. Although most internal modes do not change significantly from 90 to 250 K, the symmetric stretching mode of water at 3092 cm-1 broadens slightly and decreases appreciably in peak intensity.