Structural and electronic properties of the planar C-skeleton polymers

Atomic arrangements and electronic properties of two-dimensional C-based compounds having the diamondlike skeletons terminated with hydrogen atoms and/or hydroxyl groups, named graphane (poly-C2H2) and planar polymethanol (poly-C2OH2), have been investigated using first-principles calculations within the density functional theory. These planar polymers have direct gaps of 3.32 eV (only with hydrogen terminators) and 1.88 eV (with hydrogen and OH terminators), while crystalline diamond has an indirect band gap. The optical dipole transition between band edges, especially for the planar polymethanol, can be allowed.