Mechanically ductile 3D sp–sp2 microporous carbon

A new sp–sp2-hybridized tetragonal carbon allotrope, namely Tetra-carbon, is predicted through the evolutionary particle swarm structural search. Tetra-carbon has a 3D framework composed of sp2 carbon helixes connected by linear sp carbon chains, similar to the interconnected network of propadienyl groups, which forms the well-proportioned microporous structure. Tetra-carbon is thermodynamically more stable than known graphdiyne and carbyne carbon and also shows mechanical and dynamic stabilities at ambient pressure. Tetra-carbon is a semiconductor with an indirect band gap of 3.27 eV and has anisotropic tensile strengths with an unexpected large tensile strain of 0.64 along the [001] direction. Base on the analysis of Poisson’s ratios as well as the tensile strains, it is significantly revealed that Tetra-carbon is a mechanically ductile microporous carbon allotrope in contrast with the known brittle carbons such as diamond, potentially applied in the fields where the ductile metals are available.