科研之友
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摘要
A new metallic superhard carbon allotrope C-5 with five carbon atoms per unit cell is theoretically predicted to be stable at ambient pressure through first-principles calculations combined with unbiased swarm structure searching techniques. This novel carbon allotrope consisting of a mixture of sp(2) and sp(3) carbon network exhibits excellent mechanical properties with claimed hardness of 58.5 GPa. Results from our calculated strain-stress relationship reveals that the failure mode of crystal lattice for C-5 is dominated by shear type in the (010)[101] direction with shear stress magnitude of 74.3 GPa. The calculated electronic band structure of C-5 suggests its metallic nature. Detailed analyses of band decomposed charge density show that the metallic nature is contributed by the sp(2) carbon atoms, which form conducting pathways along the a- and b-axes.
