CATION DOPING IN HOBA2CU4O8

Computer simulation techniques have been used to obtain the potential parameters for HoBa2Cu4O8 by the 'relaxed' fitting approach and to stu dy Zn, Ce, Pr, Th, Ca, Sr, Fe, Co and Ni doping in HoBa2Cu4O8. We pred ict that Sr energetically prefers to substitute at the Ba site; Ce, Pr and Th prefer to substitute at the Ho site; and Zn, Fe, Co and Ni ene rgetically favour the Cu(2) site. Our results also suggest that Ca may substitute at the Cu(2) site or the Ba site. The structural changes a nd interatomic distances caused by these dopants were presented and an alysed. Comparing with the trends in the structural changes, interatom ic distances and interlayer distance of these dopants in YBa2Cu4O8, we predict that Sr-doped HoBa2Cu4O8 enhances T-c while the dopants Zn, C e, Pr, Th, Fe, Co and Ni depress T-c in HoBa2Cu4O8. (C) 1997 Elsevier Science Ltd. All rights reserved.