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  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.
This work was supported by National Natural Science Foundation of China (NSFC) (51421091, 51472213, 51332005, 51525205, and 51672238).
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