High-throughput design of three-dimensional carbon allotropes with Pmna space group

284 carbon allotropes with Pmna space group (No. 53) are proposed based on high-throughput calculations and density functional theory. Out of 14,285 initially identified candidates, 284 carbon allotropes are confirmed by structure optimization, removal of repetitive structures, calculation of relative enthalpies, and verification of the mechanical and thermal stabilities. Among them, 135 are metals, 55 are direct band gap semiconductors (in 15 cases with a band gap between 1.0 and 1.5 eV), 46 have three-dimensional conductive channels, 32 are superhard, and 3 are type-I Dirac semimetals.