Site determination of oxygen inB6O by oxygenKα x-ray-emission spectroscopy

An electron-excited x-ray-emission spectrum of oxygen Kα is presented for boron suboxide ${\mathrm{B}}_6$O (isostructural with ${\mathrm{B}}_{13}$ ${\mathrm{C}}_2$). The spectrum is compared with those calculated by the discrete-variation Xα (DV-Xα) method with various O-O distances as an adjustable parameter in the fixed icosahedral ${\mathrm{B}}_{12}$ framework. The observed spectrum is reproduced well when the O-O distance is in the range 2.5–3.5 Å. This O-O bond length is more than twice as long as that of a free ${\mathrm{O}}_2$ molecule. The oxygen atom is located very close to the center of the boron triangle (closed three-center bond). These results support the structure determined by x-ray structural analysis.