期刊
PHYSICAL REVIEW LETTERS
卷 113, 期 9, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevLett.113.095501
关键词
-
资金
- Defense Advanced Research Projects Agency [W31P4Q-13-1-0010]
- Army Research Laboratory [W911NF-12-2-0022]
Boron carbide (B4C) 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 (01 (1) over bar(1) over bar)/<(1) over bar 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 B4C.
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