THE ROLE OF CU-O CHAIN FRAGMENTS IN THE REBA(2)CU(3)O(6-T-C SUPERCONDUCTORS(X) HIGH)

We study the properties of the ensemble of Cu-O chain fragments that f orm on the oxygen deficient planes of the REBa(2)Cu(3)O(6+x) (REBCO) c ompounds. The chain fragments have an important role in the hole dopin g of the superconducting planes. The physics of the Cu-O chain fragmen ts themselves is interesting and can be analyzed in terms of an effect ive ASYNNNI model derived microscopically.