Birefringence of CaCO₃and Electronic Polarizabilities of the Constituent Ions

The birefringence of CaCO 3 is discussed taking account of dipole interaction among the Ca ++ and CO 3 - -ions. The electronic rolarizabilities of the CO 3 - -ions are obtained as α 1 =3.18 ×10 -24 cm 3 and α 2 =4.20 ×10 -24 cm 3 in the direction parallel and perpendicular to the optical axes respectively for n e =1.486 and n 0 =1.658. The bond polarizabilities of C-O can be obtained as α // =1.74 ×10 -24 cm 3 and α ⊥ = 1.06 ×10 -24 cm 3 in the directions parallel and perpendicular to the direction of the line connecting C and O respectively with anisotropic ratio α // /α ⊥ =1.64.