Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide

Report No. ARL-TR-7318
Authors: Amol B Rahane; Jennifer S Dunn; Vijay Kumar
Date/Pages: June 2015; 38 pages
Abstract: In this report, we use density functional theory to determine the effect of carbon (C) contamination on the electronic structure and elastic properties of boron suboxide (B6O. The electron localization surface identified 3 distinct bonding regions: 1) short, highly covalent, Bp - Bp bonds connecting 2 icosahedra; 2) ionic bonding between the equatorial boron (B) and oxygen (O); and 3) intra-icosahedral boron (Bp- Be) bonding. When C is doped at an oxygen site, the sp2 hybridized carbon forms bonds with 3 neighboring equatorial Be atoms, and the elastic moduli decrease between 0.4% and 1.7%. If 2 carbon atoms are doped at 2 neighboring oxygen sites, both carbon atoms become sp2 hybridized and the bulk modulus increases by 0.3%, yet the shear and Young's modulus decrease by 0.5%. When an interstitial atom is placed between these 2 carbons, forming C-B-C or C-C-C chains, the terminal carbons become tetrahedrally "sp3 like" bonded. By promoting the formation of a local B4C-like structure, it may be possible to improve the mechanical stability and elastic properties of B6O.
Distribution: Approved for public release
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Last Update / Reviewed: June 1, 2015