ELECTRIC-FIELD GRADIENT AT OXYGEN SITES IN RBCO - EFFECTS FROM A POSITIVE MUON

A limited quantum chemistry approach has been used to examine changes to the electric-field gradient at oxygen sites in rare-earth barium co pper oxides (RBCO) due to a bonded muon (or hydrogen). Results are rep orted for an all electron, extended basis set calculation for an OMu- molecule which is embedded in various point charge clusters to simulat e the RBCO crystal environment. Differences between the gradients for O2- and OMu- are examined for five likely muon bond sites. In each cas e the muon significantly modifies the calculated gradient.