  Most of hydrocarbons are either molecular structures or linear polymeric
chains. Discovery of graphene and manufacturing of its monohydride -- graphane
incite interest in search for three-dimensional hydrocarbon polymers. However
up to now all hypothetical hydrocarbon lattices significantly lose in energy to
stacked graphane sheets and solid benzene. We propose completely covalently
bonded solid carbon monohydride whose density significantly exceeds one of its
isomers (graphane, cubane, solid benzene). Ab-initio calculation demonstrates
that the cohesion energy of this structure at least is not worse than the
energy of graphane and benzene. In some aspect the crystal structure of
hydrocarbon presented can be regarded as a sublattice of diamond, but with the
symmetry of P-3 space group (lattice parameters a ~ 6.925 A, c ~ 12.830 A) and
Z=42 formula units per unit cell. This structure (if synthesized) may turn out
to be interesting to applications.
