Electronic structure and optical properties of Si-containing icosahedral boron crystals

Abstract

The electronic structure and the optical properties of two models of (Bi{sub 10}Si{sub 2})Si{sub 2} icosahedral crystal are studied by first-principles local-density calculations. Both models have a central Si-Si chain as in the rhombohedral B{sub 12}P{sub 2} crystal and two Si atoms replacing two B atoms in the B{sub 12} icosahedron. Model I has a Si-Si link between the substituted icohasedra, while model II does not have such a link. Both are found to be semiconductors with gaps of 1.29 and 1.72 eV, respectively. Model I is found to have a slightly lower total energy. The calculated electronic and optical properties are compared with other B-rich compounds with a similar rhombohedral structure. {copyright} {ital 1998} {ital The American Physical Society}