Further illustration of "electronic ↔ crystal structure" relationship focusing on the tetrahedral C(sp 3 )-like carbon as the building unit of the novel allotropes, can be provided by the charge density projections. Fig. shows the charge density volumes (yellow) with perfect sp 3 tetrahedral shape around carbon. For the two body-centered orthorhombic (Imm2) and body-centered tetragonal (I4m2) allotropes, the primitive cells with 12 carbon atoms are represented. Due to simple trigonal C 6 the stacking of tetrahedra is most clearly demonstrated among the three projections, with the tetrahedral yellow volumes.