  We consider a new C2H nanostructure based on bilayer graphene transformed
under the covalent bond of hydrogen atoms adsorbed on its external surface, as
well as compounds of carbon atoms located opposite each other in neighboring
layers. They constitute a "film" of the <111> diamond with a thickness of less
than 1 nm, which is called diamane. The energy characteristics and electron
spectra of diamane, graphene, and diamond are calculated using the density
functional theory and are compared with each other. The effective Young's
moduli and destruction thresholds of diamane and graphene membranes are
determined by the molecular dynamics method. It is shown that C2H diamane is
more stable than CH graphane, its dielectric "gap" is narrower than the band
gap of bulk diamond (by 0.8 eV) and graphane (by 0.3 eV), and is harder and
more brittle than the latter.
