The title compound has been synthesized. On the basis of the determined single-crystal structure data of this compound, the electronic structures are calculated using the INDO/S method with configuration interactions, following combination with the sum-over- state method. The linear polarizability of micro-species Ca2B2O5 is obtained, and the average refractive index is estimated for bulk Ca2B2O5. It is shown that the valence band has the contributions from the 2p orbitals of B and O atoms, while the low edge of conduction band has the main contributions from the Ca atoms, and the charge transfers from the oxygen atomic orbital to calcium atomic orbital make the significant contributions to the polarizability.

Key words: BORATES, ELECTRONIC STRUCTURE, BAND STRUCTURES, CALCIUM COMPOUDS, CHARGE TRANSFER