科研之友
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摘要
Carbon is the basis of life on Earth and many technological applications. We computationally report an sp(3)-hybridization-assembled carbon allotrope constructed by helical triangle chains through the evolutionary structure prediction method. Different from the previous metallic carbon K4, this carbon, called Tri-carbon, is mechanically and dynamically stable at ambient pressure. High ring strain in the carbon triangle blocks forces the C-C bond in Tri-carbon to be a 'bent bond', rather than the common single bond in diamond or the p bond in graphite. Unlike the unstrained sp(3)-hybridization in semiconductive diamond, valence electrons in the 'bent bond' are recombined to form extremely anisotropic sp(3)-hybridized bonds, thus conferring metallicity to Tri-carbon. Under nonhydrostatic conditions, Tri-carbon shows significantly anisotropic ideal tensile and compressive strength. Tri-carbon is expected to be achieved through chemical methods, such as the synthesis of cyclopropane derivatives (e. g. triangulane and tetrahedrane). These methods eliminate the restriction of ultra-high pressure to obtain metallic carbons.
