Assessment of the possibility of band gap widening of BaSi2 by incorporation of carbon

Abstract In order to assess the possibility of band gap widening of semiconducting BaSi 2 , effect of carbon incorporation into the BaSi 2 lattice was evaluated by first-principle calculations. At first, structures of the equilibrium and the hypothetical BaSi 2 , BaC 2 , and BaSiC with the BaSi 2 type or the CaC 2 type structures are geometrically optimized and their most probable structures have been determined by energetic evaluations. As for BaC 2 and BaSi 2 , their equilibrium structures are properly predicted. As for BaSiC, the BaSi 2 type structure with the Si (5) (8d) sites substituted by carbon seems to be more favorable than (A), the BaSi 2 type structure with the Si (3) (4c) and Si (4) (4c) sites are substituted by C and than (B), the CaC 2 type structure. However, incorporation of C into BaSi 2 seems not energetically favorable and would not proceed so much. In order to asses the case of diluted carbon concentration, dependence of the band gap on the carbon concentration was evaluated using the models of Ba(Si 1− x C x ) 2 with the BaSi 2 type structure where their Si (5) (8d) sites were partly substituted by carbon. In case compounds with x > 0.1 are formed, a band gap widening of BaSi 2 can be expected.