Alkali carbonates: Raman spectroscopy, ab initio calculations, and structure

Equilibrium structures of Li 2 CO 3 and K 2 CO 3 were calculated using ab initio molecular orbital calculations carried out at the Hartree-Fock (HF) level. Of the four structures considered for Li 2 CO 3 and K 2 CO 3 , the most stable was a structure with all five atoms in a plane. The harmonic frequencies were also calculated and found to be in agreement with the present Raman measurements. Structure factors, calculated from the ab initio data for each of the four structures considered, are compared with existing X-ray results.