Electronic structure of the High-T sub c superconductor Ba sub (1-x) K sub x BiO sub 3.

The results of electronic-structure calculations for ordered Ba sub (0.5) K sub (0.5) BiO sub 3 alloys confirm that the antibonding Bi(6s)-O(2p) conduction band near E sub F in the cubic BaBiO sub 3 is minimally affected by substitutional K doping at the perovskite A (Ba) site. This supports the prediction that such A-site doping would extend the metallic range closer to half-filling (BaBiO sub 3) than B-site doping (BaPb sub (1-y) Bi sub y O sub 3), placing E sub F in a range where increased coupling of the conduction electrons to bond-stretching O phonons would lead to enhanced superconducting transition temperatures. We suggest that Ba sub (1-x) T sub x PbO sub 3, where T is trivalent, might also exhibit favorable superconducting properties.