Band structure of La2NiO4.25 (La8Ni4O17)
Abstract
The monoelectronic band structures of
La
8
Ni
4
O
17
at 9 and 300 K are calculated
using the extended Hückel tight-binding method. Within a rigid band
hypothesis and discussing the location of the Fermi level, we obtain band
diagrams which corroborate experimental data such as the evolution of the
Curie constant and Ni–O bond length distributions with temperature,
as well as the assumptions of (a) hopping-type conductivity in
narrow bands, with at least two type of carriers, (b) a mixed
valence for nickel ranging from +I to +III, (c) a charge-transfer
equilibrium, displaced with temperature, (d) the occurrence of
(O
3
)
5-
entities (O
apex
–O
interstitial
–O
apex
), although the
O
2-
hypothesis for all oxygen ions in the structure can
not be excluded within this study.
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