A solid phase or form of carbon is based on fullerenes with thirty six carbon
atoms
(C36). The C36 structure with D6h symmetry is
one of the two most energetically favorable, and is conducive to forming a periodic
system. The lowest energy crystal is a highly bonded network of hexagonal planes
of C36 subunits with AB stacking. The C36 solid is not a
purely van der Waals solid, but has covalent-like bonding, leading to a solid with
enhanced structural rigidity. The solid C36 material is made by synthesizing
and selecting out C36 fullerenes in relatively large quantities. A C36
rich fullerene soot is produced in a helium environment arc discharge chamber
by operating at an optimum helium pressure (400 torr). The C36 is separated
from the soot by a two step process. The soot is first treated with a first solvent,
e.g. toluene, to remove the higher order fullerenes but leave the C36.
The soot is then treated with a second solvent, e.g. pyridine, which is more polarizable
than the first solvent used for the larger fullerenes. The second solvent extracts
the C36 from the soot. Thin films and powders can then be produced from
the extracted C36. Other materials are based on C36 fullerenes,
providing for different properties.