On the existence of tetragonal boron and the crystal structures of B50C2 and B50N2: an x-ray diffraction analysis

Abstract

Abstract “I-tetragonal boron” of the literature is in fact a higher boron carbide or boron nitride. We have studied two crystals of composition B50C2 and B50N2 by x-ray diffraction analysis and determined the precise electron densities to R = 5.4%. Four icosahedra in the unit cell are bridged by two carbon or nitrogen atoms respectively at 2b in 001/2; 1/21/20. Two boron atoms fill the large holes between the icosahedra in a statistical way providing connections between two icosahedra.