Crystal Structure of Na2M2(BO3)2O (M=Al, Ga); Comparison with Other Layered Oxyborates and SiP2O7

Unpolarized Raman spectra of policrystalline samples of calcium (II)-copper (II) formate [CaCu(HCOO)4] and dicalcium (II)-copper (II) formate [Ca2Cu(HCOO) 6] were recorded and analyzed in the temperature range from 30 to 300 K. The observed modes at 300 K were assigned on the basis of formate group vibrations and correlations with previous data reported for other formate compounds. The splitting of the internal HCOO modes agrees with the group theory predictions. No changes either in the wavenumber or intensity of Raman modes were observed when the temperature of the samples was cooled to 30 K. This indicates that these compounds do no exhibit any phase transformation in the temperature range investigated.