Abstract
Due to a large discrepancy between theory and experiment, the electronic character of crystalline boron carbide has been a controversial topic in the field of icosahedral boron-rich solids. We demonstrate that this discrepancy is removed when configurational disorder is accurately considered in the theoretical calculations. We find that while the ordered ground state is metallic, the configurationally disordered , modeled with a superatom-special quasirandom structure method, goes through a metal to nonmetal transition as the degree of disorder is increased with increasing temperature. Specifically, one of the chain-end carbon atoms in the CBC chains substitutes a neighboring equatorial boron atom in a icosahedron bonded to it, giving rise to a (BBC) unit. The atomic configuration of the substitutionally disordered thus tends to be dominated by a mixture between (CBC) and (BBC). Due to splitting of valence states in (BBC), the electron deficiency in (CBC) is gradually compensated.
2 More- Received 2 February 2015
- Revised 19 May 2015
DOI:https://doi.org/10.1103/PhysRevB.92.014202
©2015 American Physical Society