THE STRUCTURE OF LIKCO3 STUDIED BY AB-INITIO CALCULATIONS AND RAMAN-SPECTROSCOPY

The equilibrium structures of the LiKCO3 monomer and dimer were derive d from ab initio calculations. The most stable cation site in the equi librium structure of the LiKCO3 monomer is the 'edge' site of the CO32 - ion, which is similar to our previous results for Li2CO3 and K2CO3. Moreover, the structure with Li at the 'edge' site and K at the 'corne r' site was found to have a low energy. The vibrations of both these g eometries were calculated and compared with the measured Raman spectru m for monoclinic LiKCO3. Harmonic vibrational frequencies derived from these geometries could not be assigned to the measured Raman bands, w hich showed split v(1) and v(3) bands. Therefore, the LiKCO3 dimer was examined. Harmonic vibrational frequencies derived from the equilibri um structure of LiKCO3 dimer showed two split v(1) bands and four v(3) bands which are in good agreement with the measured Raman spectrum. ( C) 1998 Elsevier Science Ltd. All rights reserved.