Stabilization of the Ti3Co5B2-type structure for Ti3-xSixRu5B2 through Si-Ti substitution

We report a route for designing and synthesizing Ti3CO5B2-type compounds in the Ti-Ru-B system by using chemical substitution of Si for Ti to decrease the d-electron-based antibonding interactions that it is argued would otherwise drive an instability in this structure for unsubstituted Ti3Ru5B2. Ti3-xSixRu5B2 with x=0.75, 1.00 and 1.25 nominal compositions crystalizes in the Ti3CO3B2 structure type using arc melting methods, whereas at lower doping levels (x=0.0, 0.25 and 0.50) the more complex Zn11Rh18B8-type structure is stable. Electronic structure calculations show that in hypothetical, unsubstituted Ti3Ru5B2 with the Ti3CO5B2-type structure, the antibonding interactions are strong around the Fermi level between the Ti and Ru in the structure that form tetragonal prisms. We propose that weakening these strong interactions through the partial substitution of isovalent Si for Ti leads to the observed stability of the Ti3CO3B2-type structure for Ti3-xSixRu5B2 for x approximate to 1. Published by Elsevier Inc.