2022/10/09 by Matar, Samir F
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci)
paper · doi:10.48550/arxiv.2210.04210
From crystal chemistry rationale and density functional DFT calculations, novel tetragonal carbon C5 is proposed as simplest ultrahard allotrope with mixed hybrid carbon hybridizations (sp2 - sp3). Novel pentacarbon is identified as cohesive and stable both dynamically and mechanically. Whereas charge density is localized about tetrahedral C-sp3, it is found delocalized around trigonal C-sp2 resulting in metallic behavior. The anisotropic structure characteristics caused by the aligned trigonal carbon along the tetragonal c-axis provide high Vickers hardness with a magnitude close to diamond