H. Oesterreicher, LOCAL MODEL FOR CHARGE DELOCALIZATION IN PARTLY SUBSTITUTED CUPRATE SUPERCONDUCTORS, Materials research bulletin, 30(8), 1995, pp. 987-993
Partial substitutions according to YBa2(Cu(1-x)M(x))(3)O-y with M = Ni
etc. in connection with various redox sequencings allow for complex s
trategies in obtaining novel materials. We analyze redox related struc
tural data on selected model compounds with special emphasis on a new
local structural approach, derive aspects of their electronic behavior
, and gain an expanded understanding of the charge balance function of
Cu(1). We elaborate on the conditions for antitypes to conventional b
ehavior such as n type superconductivity at low y and semiconductivity
at high y. We show that a localization catastrophe can occur when the
population of(1)4 configurations (Cu(1) coordinated by 4 O) is low. I
n this case (1)3 and (1)2 coordinations dictate the spatial behavior o
f (1)4 which leads to charge localization. We show that this correspon
ds to a Mott type transition which has a general implication in degrad
ing superconducting properties on further reoxygenation.