Configurational orderdisorder induced metalnonmetal transition in B1_{3}C_{2} studied with firstprinciples superatomspecial quasirandom structure method
Abstract
Due to a large discrepancy between theory and experiment, the electronic character of crystalline boron carbide B_{13}C_{2} has been a controversial topic in the field of icosahedral boronrich 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 B_{13}C_{2} is metallic, the configurationally disordered B_{13}C_{2} , modeled with a superatomspecial quasirandom structure method, goes through a metal to nonmetal transition as the degree of disorder is increased with increasing temperature. Specifically, one of the chainend carbon atoms in the CBC chains substitutes a neighboring equatorial boron atom in a B_{12} icosahedron bonded to it, giving rise to a B_{11}C^{e} (BBC) unit. The atomic configuration of the substitutionally disordered B_{13}C_{2} thus tends to be dominated by a mixture between B_{12}(CBC) and B_{11}C^{e} (BBC). Due to splitting of valence states in B_{11}C^{e} (BBC), the electron deficiency in B_{12}(CBC) is gradually compensated.
 Publication:

Physical Review B
 Pub Date:
 July 2015
 DOI:
 10.1103/PhysRevB.92.014202
 arXiv:
 arXiv:1508.07848
 Bibcode:
 2015PhRvB..92a4202E
 Keywords:

 64.60.Cn;
 64.60.De;
 81.30.Hd;
 61.50.Ks;
 Orderdisorder transformations;
 statistical mechanics of model systems;
 Statistical mechanics of model systems;
 Constantcomposition solidsolid phase transformations: polymorphic massive and orderdisorder;
 Crystallographic aspects of phase transformations;
 pressure effects;
 Condensed Matter  Materials Science
 EPrint:
 Phys. Rev. B 92, 014202 (2015)