▎ 摘　　要

The net-Y, a novel two-dimensional carbon allotrope with four-, six-and eight-membered rings, is investigated by performing first-principles calculations. The calculations on structural stability unambiguously prove that net-Y is an energetically metastable, dynamically and thermally stable phase, and it can also be buckled about 0.4 angstrom. We find that the net-Y exhibits strong mechanical anisotropy, and the inplane Young's modulus of net-Y along a and b directions is found smaller than graphene but comparable with that of j-graphene and penta-graphene. Meanwhile, the net-Y possesses intrinsic metallicity with high carrier velocities comparable to that of graphene (similar to 10(6) m/s). Excitedly, a possible synthetic route towards net-Y from graphene-like nanoribbons embedded four-and eight-membered rings is achieved by first-principles molecular dynamics simulations, indicating that the realization of net-Y is not impossible. Moreover, two three-dimensional (3D) stable close-packed net-Y carbon allotropes are also proposed. Unlike the metallic 3D planar net-Y, the 3D buckled net-Y is a superhard indirect bandgap semiconductor, which further broadens the application potential of net-Y. (C) 2018 Elsevier Ltd. All rights reserved.