A theoretical study of the molecule of boric oxide B₂O₃

Conclusion

At the present time there is definite experimental material on the geometric configurations and vibrational frequencies for molecules and ions of the type X₂Y₃, namely: B₂O₃, Xe₂F ⁺₃ [29], I ⁻₅ [30, 31], H₂F ⁺₃ [32], etc. All of them, within the limits of accuracy of the experimental data, have a planar geometric configuration YXYXY, and the angle XYX, with the exception of I ⁻₅ , is close to 135° (137.5, 151.95, and 130–139° in the series given above), the angle YXY is close to 180° (174–178°), and the distance from a terminal atom Y to the neighboring atom X is approximately 10% shorter than the corresponding distance from the central atom Y to the neighboring atoms X. The estimated frequency of the bending vibration has comparatively low values: 70–100 cm⁻¹ for B₂O₃ in a matrix, and ∼160 cm⁻¹ for XeF ⁺₃ in the crystal. These data indicate the existence of a class of deformationally nonrigid molecules of the type X₂Y₃, which must contain other molecules in addition to those listed above. The detailed study of this class of compound will make it posible to answer a number of questions which have not yet been resolved, for example those associated with the difference in the composition of the vapor over B₂O₃ and Al₂O₃, etc. The experience of the present work shows that such a study should include, as a natural and necessary component, quantum-mechanical calculations, whose results generally make it possible to resolve disputed problems, to establish a correspondence between different experimental data, and to obtain information on the structure of potential surfaces and the electronic structures of different states of the molecules being studied, which cannot yet be obtained experimentally.