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Asymmetric twins in boron rich boron carbide

Yang, Xiaokun and Goddard, William A., III and An, Qi (2018) Asymmetric twins in boron rich boron carbide. Physical Chemistry Chemical Physics, 20 (19). pp. 13340-13347. ISSN 1463-9076. doi:10.1039/c8cp01429a.

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Twin boundaries (TBs) play an essential role in enhancing the mechanical, electronic and transport properties of polycrystalline materials. However, the mechanisms are not well understood. In particular, we considered that they may play an important role in boron rich boron carbide (B_(vr)BC), which exhibits promising properties such as low density, super hardness, high abrasion resistance, and excellent neutron absorption. Here, we apply first-principles-based simulations to identify the atomic structures of TBs in B_(vr)BC and their roles for the inelastic response to applied stresses. In addition to symmetric TBs in B_(vr)BC, we identified a new type of asymmetric twin that constitutes the phase boundaries between boron rich boron carbide (B_(13)C_2) and B_(vr)BC (B_(14)C). The predicted mechanical response of these asymmetric twins indicates a significant reduction of the ideal shear strength compared to single crystals B_(13)C_2 and B_(14)C, suggesting that the asymmetric twins facilitate the disintegration of icosahedral clusters under applied stress, which in turn leads to amorphous band formation and brittle failure. These results provide a mechanistic basis towards understating the roles of TBs in B_(vr)BC and related superhard ceramics.

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Goddard, William A., III0000-0003-0097-5716
An, Qi0000-0003-4838-6232
Additional Information:© 2018 the Owner Societies. The article was received on 04 Mar 2018, accepted on 12 Apr 2018 and first published on 13 Apr 2018. This work was supported by the National Science Foundation (CMMI–1727428, program manager, Siddiq Qidwai). Conflicts of interest: There are no conflicts to declare.
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Issue or Number:19
Record Number:CaltechAUTHORS:20180502-085707003
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86187
Deposited By: Tony Diaz
Deposited On:03 May 2018 21:20
Last Modified:15 Nov 2021 20:36

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