L. Duclaux et al., DETERMINATION OF THE LOW-TEMPERATURE 2D AND 3D STRUCTURES OF THE 2ND STAGE CESIUM GRAPHITIDE, Journal of physics and chemistry of solids, 57(6-8), 1996, pp. 733-740
The structure of stage-2 cesium derivatives CsC24 was investigated usi
ng X-ray diffraction. The 2D and 3D arrangements of the cesium atoms i
n pure CsC24 were deduced from Laue diffractograms and rotating crysta
l patterns. Below 165K, the 2D structure is formed mainly of a 2.54 x
2.59 R 14.5 degrees incommensurate structure with 2 x 2 R 0 degrees co
mmensurate domains. At 140 K, while the cesium incommensurate layers g
et 3D stacked, the 2 x 2 R 0 degrees commensurate layers are randomly
distributed in the structure. The incommensurate cesium layers are arr
anged in a 2D modulated stacking, but at lower temperatures this struc
ture is partially replaced by a rhombohedral stacking in which the ces
ium atoms are modulated along the c-axis owing to the dominating influ
ence of graphitic host. In slightly oxidized compounds, the presence o
f impurities induces the formation of additional 2.23 x 2.23 R 25.5 de
grees incommensurate domains which are separated from the structures a
lready observed in pure compounds. These stage-2 domains of compositio
n CsC20 are characterized by a large interlayer distance. We suggest t
hat oxygen suboxide impurities at the edge of the domains are at the o
rigin of this particular dense structure.