[15a-A403-1~11] 17.1 Carbon nanotubes & other nanocarbon materials

[15a-A403-10] Design of a three-dimensional carbon allotrope comprising fused pentagons

〇(M2)Yasumaru Fujii¹, Mina Maruyama¹, Nguyen Thanh Cuong¹, Susumu Okada¹ (1.Univ. of Tsukuba)

Keywords:diamond, material design

A pentagonal covalent network consisting of sp2 and sp3 C atoms were investigated based on the density functional theory. These theoretical investigations clarified that this pentagonal covalent network is a stable three-dimensional carbon allotrope with the Fm3-m space group that possesses a 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 1692 and 1115 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 the L and X points for valence and conduction band edges, respectively, with relatively small carrier masses.