To illustrate furthermore the "electronic  crystal" structure relationship, the projections of the charge density on the atomic constituents were undertaken. The high precision calculations (k-mesh: k x =k y =k z =10) providing the CHGCAR output file were analyzed with VESTA academic software . For C 16 , Fig. shows the charge density volumes (yellow) around C with perfect sp 3 tetrahedral shape. For B 8 N 8 (Fig. ) the projections show a large localization around N that can be assigned to the iono-covalent character of the bonds in boron nitride arising from the large difference of electronegativities between B and N: B = 2.04 versus N = 3.04 (while C = 2.55).