Now, a theory put forth nearly 20 years ago seems to explain why PWD correlates so strongly with Tc.
In the mid 1990's Howard Blackstead of Notre Dame and John Dow of A.S.U., postulated that oxygen located in the "chain layer" of a crystal lattice was being compressed into a metallic superconducting state.
To quote: "Experimental evidence indicates that the holes of the hypocharged oxygen in the charge-reservoir regions contribute primarily to the superconductivity, contrary to most current models of high-temperature superconductivity, which are based on superconductivity originating in the cuprate-planes.
