An orthorhombic superhard carbon allotrope: Pmma C24

The simplest dense carbon allotrope: Ultra-hard body-centered tetragonal C4

“…Presently proposed tet-C 4 exhibits hardness and fracture toughness magnitudes very close to those of diamond (both cubic and hexagonal). It should be also noted that hardness of tet-C 4 is much higher than H V -values reported for all recently predicted carbon allotropes [5][6][7]. A good agreement can be noted.…”

“…Our proposition of a very simple dense carbon allotrope, i.e. with four atoms in a body-centered tetragonal unit cell (Z=2), knowing that diamond has face-centered cubic unit cell (Z=4), is challenging in view of the recently predicted carbon allotropes of large stoichiometries (C 16 , C 24 and C 36 [5][6][7]).…”

Novel ultra-hard hexacarbon allotropes from first principles

“…Thus, all three C 6 allotropes have exceptional mechanical properties among all recently proposed carbon allotropes [29][30][31][32][33] and thus can be considered as prospective ultra-hard materials [1].…”

“…On the other hand, hardness of these phases is much higher than hardness of the vast majority of recently predicted carbon allotropes (C 14 , C 16 , C 24 , C 36 , etc.) [29][30][31][32][33].…”

Theoretical Investigations of a BN Polymorph with sp2 + sp3 Hybridizations

“…A directional dependence can visually show the anisotropic characteristics due to the varying Young's moduli generated in different planes. The three-dimensional (3D) surface is a regular sphere, which means that the material is isotropic; otherwise, the material shows anisotropic characteristics [8,[51][52][53][54][55], and the smaller the resemblance to a sphere, the larger the anisotropy, to evaluate the mechanical anisotropy properties of E.…”