To illustrate the electron distribution within the new boron nitrides, the analysis was extended to a qualitative representation of the charge densities. Figs. and (right panels) represent the charge density projections with yellow volumes around the atoms. In all cases, the charges are concentrated around nitrogen atoms (gray spheres). In fact, boron nitride is a polar covalent compound with significant charge transfer to N, which is characterized by an electronegativity of N=3.04 while B=2.04 according to the Pauling scale. In B 2 N 3 , the charge gray volumes are squeezed toward the next cell along the vertical c direction, corresponding to the N-N connexions between successive cells. By introducing new B-N bonds, equiatomic tet-B 3 N 3 and h-B 3 N 3 are created, and the charge volumes are around N atoms in both symmetries.