Multipole refinement and electron density analysis in natural borosilicate datolite using X-ray diffraction data.

The electron density distribution in the layer silicate datolite, Ca[BOH(SiO4)], was analyzed using high-precision single-crystal X-ray diffraction data (Mo Kalpha, T=293 K). The Hansen-Coppens multipole model and Bader's topological analysis of the electron density provides a basis for the quantitative characterization of the bonded interaction of datolite. The results are presented both in the form of maps of the electron density distribution and its Laplacian, and in a compact way in terms of the critical points of the electron density. The relative electronegativities are also discussed. It was shown that closed-shell type interactions exist between Ca and O atoms, whereas Si-O and B-O bonds exhibit an intermediate nature with a strong covalent component. An analysis of the topology of the electrostatic potential demonstrates the relevance of considering this physical property to obtain a complete picture of structure-forming factors.