G. Baldinozzi et al., INCOMMENSURATE MODERATED DISORDER IN BA0.85CA2.15IN6O12, Acta crystallographica. Section B, Structural science, 52, 1996, pp. 780-789
The tunnel structure of the oxide Ba0.85Ca2.15In6O12 has been revisite
d. A mono-incommensurate modulation has been evidenced by electron dif
fraction. The simultaneous refinement of X-ray and neutron powder diff
raction patterns has allowed a complete determination of the incommens
urate structure [P3(1/3 1/3 gamma)]. The existence of a modulated diso
rder, affecting Ba and Ca atoms, has been pointed out. The occupancy m
odulation concerning Ba and Ca atoms located on the hexagonal tunnel a
xis induces a modulation of the Ba-O bond lengths. The high-resolution
electron microscopy study has shown the existence of twinning domains
and of crystal regions possessing a defective arrangement of the modu
lation.