Synchrotron powder diffraction Rietveld refinement of MgB20 crystal structure

The crystal structure of MgB20 has been investigated by X-ray and synchrotron powder diffraction at room temperature. As it happens in other metal-boron systems, the Rietveld refinement of this magnesium boron-rich phase shows a structure derived directly from β-boron. The substantially unaltered B–B framework hosts magnesium atoms in three different atomic positions (D, E and F holes); the occupancy of these sites is partial. The resulting unit cell is trigonal with space group R3m, the refined hexagonal axes a=1.09830(4) and c=2.41561(15) nm.