Retraction: Pentadiamond: A Hard Carbon Allotrope of a Pentagonal Network of sp2 and sp3 C Atoms (Physical Review Letters (2020) 125 (016001) DOI: 10.1103/PhysRevLett.125.016001)

Abstract

A pentagonal covalent network consisting of sp2 and sp3 C atoms has been investigated based on the density functional theory. Our theoretical investigations clarified that the pentagonal covalent network is a metastable three-dimensional carbon allotrope with the Fm¯3m space group possessing remarkable mechanical properties: relatively high bulk modulus of 381 GPa together with a negative Poisson’s ratio of -0.241 . Accordingly, the pentagonal covalent network possesses extremely high Young’s and shear moduli of 1691 and 1113 GPa, respectively, surpassing those of the diamond. The electronic structure of the pentagonal network is a semiconductor with an indirect band gap of 2.52 eV between L and X points for valence and conduction band edges, respectively, with the relatively small carrier masses.