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

We present the designing and synthesizing of 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 would otherwise drive an instability in this structure for unsubstituted Ti3Ru5B2. 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 Ti3Co5B2-type structure for Ti3−xSixRu5B2 for x≈1.278