The most relevant feature in C 5 (Fig. ) is the red charge cross sections, which indicate the continuous charge density of red traces through the 8 corners toward the adjacent cells along the tetragonal c direction (vertical direction). This feature is also observed within the C 6 cell, as a signature of >C=C< with characteristic sp 2 hybridization. Going to C 7 , the central part of the unit cell contains the >C=C=C< propadiene subunit, while the >C=C< ene subunits are located between the two adjacent cells (Fig. ). However, the charge density is weaker as you move to the next cell, as shown by the green areas, which indicate less charge. This may explain why C 7 is the least cohesive of the series studied.