Electronic structure of three-dimensional graphyne

Graphyne is a hypothetical carbon allotrope with a layered structure. We ca lculated the optimized geometries and electronic structures of three-dimens ional graphyne in some possible stacking arrangements from symmetry conside rations. The optimized lattice constants and the binding energy of graphyne are given in comparison with graphite. The binding energy of graphyne is a bout 90% of that of graphite, and graphyne will be stable when it is synthe sized. The electronic structures are classified into two types, metallic an d semiconducting, according to the stacking arrangements. The most stable g raphyne is expected to be a semiconductor with a moderate band gap.