Revisit: High resolution charge density study of α-rhombohedral boron using third-generation SR data at SPring-8

• Charge density of α-boron has been investigated using the SR powder at SPring-8.
• We found the resolution dependence of charge density by MEM.
• We found that diffraction data with d > 0.4 Å resolution were needed for α-boron.
• The reason of the previous peculiar bonding feature was experimentally resolved.

Experimental charge density of α-rhombohedral boron (α-B12) by a Maximum entropy method (MEM) has been re-investigated using the high resolution powder diffraction data measured at third-generation synchrotron radiation (SR) source, SPring-8. The present MEM charge density has many discrepancies from the previous MEM charge densities reported by Fujimori et al. and Hosoi et al. The data-resolution dependence of the MEM charge density was investigated using the present data. We found that diffraction data with d > 0.4 Å resolution range were needed to reveal qualitative bonding nature of α-B12 at 100 K. The peculiar bonding natures, such as a bend B–B bond and a propeller-shaped bond, which were found in the previous studies have disappeared by using d > 0.4 Å data. The bonding nature of MEM charge density using the full data with d > 0.327 Å d-spacing range is well agreed with those of theoretical calculations. The present study suggests that resolution test is important for an accurate charge density study of boron related materials.

Figure optionsDownload as PowerPoint slide