Charge density of hexagonal boron nitride using synchrotron radiation powder data by Maximum Entropy Method

In order to explore the bonding nature of hexagonal boron nitride (h-BN), a charge density study of h-BN has been carried out by the Maximum Entropy Method (MEM) using the Synchrotron Radiation powder data. In the obtained MEM charge density distribution map, the strong directional B-N bond is found in the basal plane which corresponds to a a bond by sp² hybridization. On the other hand, appreciable charge densities are not observed in the interlayer region, indicating chemical bonding nature between the basal planes is ionic. These fundamental features show good accordance with the charge density derived from the accurate self-consistent full-potential linearized augmented-plane-wave calculation. Thus, it can be concluded that the MEM analysis successfully visualizes the image of the two-dimensional nature in the h-BN crystal. Furthermore, the quantitative examination of the charge concentration at atomic sites in the MEM charge density provides experimental evidence of charge transfer from B atoms towards N atoms.