Atomistic Explanation of Shear-Induced Amorphous Band Formation in Boron Carbide
Qi An, William A. Goddard III, Tao Cheng
Abstract
Boron carbide (B_4C) is very hard, but its applications are hindered by stress-induced amorphous band formation. To explain this behavior, we used density function theory (Perdew-Burke-Ernzerhof flavor) to examine the response to shear along 11 plausible slip systems. We found that the (011 ¯ 1 ¯ )/⟨1 ¯ 101⟩ slip system has the lowest shear strength (consistent with previous experimental studies) and that this slip leads to a unique plastic deformation before failure in which a boron-carbon bond between neighboring icosahedral clusters breaks to form a carbon lone pair (Lewis base) on the C within the icosahedron. Further shear then leads this Lewis base C to form a new bond with the Lewis acidic B in the middle of a CBC chain. This then initiates destruction of this icosahedron. The result is the amorphous structure observed experimentally. We suggest how this insight could be used to strengthen B_4C.
Group Members
An, Q., III, W. A. G., & Cheng, T. (2014). Atomistic Explanation of Shear-Induced Amorphous Band Formation in Boron Carbide. *Phys. Rev. Lett.*, *113*(9), Art. No. 095501. https://doi.org/10.1103/physrevlett.113.095501