Charge transfer and transition-metal cluster: Boron bonding in the bct superconducting Y(Rh1-xRux)4B4 system

An analysis of the bonding and charge transfer as a function of transition-metal concentration is presented for the bct superconducting system Y(Rh1-xRux)4B4. A sharp drop in the superconducting critical temperature Tc from 9.5 K to below 1.0 K near a critical concentration is not reflected in the smooth, linear variation of the single-crystal lattice parameters and B-B interatomic distances. Analysis of the boron KVV Auger data indicates the boron p-like states near the Fermi energy are increasingly populated in a continuous manner with increasing x. We find no evidence of any abrupt changes in the electronic structure near xcr.