ELECTRONIC STRUCTURE OF (B₃O₆) ^-3 CLUSTER AND ULTRAVIOLET ABSORPTION OF β-BaB₂O₄ CRYSTALS

The electronic structure and the electric dipole matrix elements of (B₃O₆) ^-3 cluster are calculated by multiple scattering X_α(MSX_α) method. The ultraviolet absorption of β-BaB₂O₄ crystal is determined from the above calculation, and the absorption edge (about 2000Å) thus estimated is in good agreement with the experimental measurement.