Specifics of Al substitution into boron carbide: A DFT study

Boron carbide (B₄C), known for its hardness and low density, is prone to local amorphization under high non-hydrostatic loads, limiting its applications. Aluminum doping is promising due to aluminum's atomic size, fitting into the B₄C crystal lattice, particularly the intericosahedra chain, potentially reducing amorphization. This work uses first-principles calculations to study aluminum placement in B₄C. We examine the potential for Al substitution in the icosahedron and intericosahedra chain, identifying possible locations. Results show that aluminum can't replace atoms in the icosahedron, but substituting one central atom in the intericosahedra chain with aluminum is energetically favorable and likely changes the chain configuration to an angular one. Additionally, aluminum can substitute one carbon in the (C-B-C) chain of B₁₂(C-B-C) boron carbide. Comparative analysis suggests these configurations may coexist. Our study offers a theoretical model that can guide future experimental efforts and provides valuable insights into the structural specifics of aluminum-doped boron carbide.