Periodic ab initio Hartree-Fock study of trigonal and orthorhombic phases of boric oxides

The structure and electronic properties of trigonal and orthorhombic boric oxide (B₂O₃) are studied using periodic ab initio Hartree-Fock method. The optimised structural parameters for two B₂O₃ polymorphs are in good agreement with experimental data. The analyses of their electronic structures provide insights into the chemical nature of the B–O bond and the way in which it changes with the coordination number around boron and oxygen. Our quantum-chemical study suggests that the orthorhombic form is more ionic than the trigonal form and that the coordination number of boron around oxygen plays a more dominant role than that of oxygen around boron in B₂O₃ crystals.