Jump to main content
Jump to site search
Access to RSC content Close the message box

Continue to access RSC content when you are not at your institution. Follow our step-by-step guide.


Issue 4, 2007
Previous Article Next Article

Structure and bonding in boron carbide: The invincibility of imperfections

Author affiliations

Abstract

Boron carbide, usually described as B4C, has the mysterious ability to accommodate a large variation in carbon composition (to as much as B10C) without undergoing a basic structural change. We systematically explore how the bonding varies with carbon concentration in this structure and the origin of the fundamental electron deficiency of the phase. As the carbon concentration is reduced, we find that the exo-polyhedral BEq–C bonds of the icosahedra in the structure become increasingly engaged in multiple bonding, and the repulsive steric interactions between the bulky B12 units surrounding the carbon atom are reduced. The short bond lengths observed within the three-atom [triple bond splayed left]C–B–C[triple bond splayed right] chains are then due to substantial π-bonding, while the carbon deficiency weakens its σ-framework significantly. We conclude that the idealized framework of boron carbide has to expel some electrons in order to maximize its bonding; disorder in the structure is an inevitable consequence of this partial oxidation. The localization of electronic states arising from the disorder leads to the semiconducting nature of boron carbide throughout its composition range.

Graphical abstract: Structure and bonding in boron carbide: The invincibility of imperfections

Back to tab navigation

Article information


Submitted
18 Dec 2006
Accepted
08 Feb 2007
First published
27 Feb 2007

New J. Chem., 2007,31, 473-485
Article type
Paper

Structure and bonding in boron carbide: The invincibility of imperfections

M. M. Balakrishnarajan, P. D. Pancharatna and R. Hoffmann, New J. Chem., 2007, 31, 473
DOI: 10.1039/B618493F

Social activity

Search articles by author

Spotlight

Advertisements