Strengthening boron carbide through lithium dopant

The high strength of boron carbide (B 4 C) is essential in its engineering applications such as wear‐resistance and body armors. Here, by employing density functional theory simulations, we demonstrated that the strength of B 4 C can be enhanced by doping lithium to boron‐rich boron carbide (B 13 C 2 ) to form r‐LiB 13 C 2 . The bonding analysis on r‐LiB 13 C 2 indicates that the electron counting rule (or Wade's rule) is satisfied in r‐LiB 13 C 2 whose formula can be written as r‐Li + (B 12 ) 2‐ (CB + C). The shear deformation on r‐LiB 13 C 2 indicates that its ideal shear strength is larger than that of B 4 C because of the existing of Li dopant. The failure process of r‐LiB 13 C 2 under ideal shear deformation initiates from breaking the icosahedral‐icosahedral B‐B bonds. Then these B atoms react with the middle B in the C‐B‐C chain, resulting in the disintegration of icosahedral clusters and brittle failure. More interesting, the nanotwinned r‐LiB 13 C 2 is even stronger than r‐LiB 13 C 2 because of the directional nature of covalent bonding at the twin boundaries. This suggests that the nanotwinned r‐LiB 13 C 2 has a significant enhanced strength compared to B 4 C. Our simulation results illustrate the deformation mechanism of Li‐doped boron carbide and its nanotwinned microstructure. We proposed to improve the strength of boron carbide by doping Li into B 13 C 2 and increasing its twin densities.