Chemistry Reference
In-Depth Information
Te-III 8.5 GPa
8
6
4
2
0
-2
2
θ
(deg.)
5
10
15
20
Fig. 9 Rietveld refinement of incommensurate Te-III at 8.5 GPa. The
upper
and
lower tick marks
below the profile mark the peak positions of the main and first order satellite reflections, res-
pectively. The reflections shown in Fig.
8
are identified by their (
hklm
) indices, where the main
reflections are indexed (
hkl
0)
½
½
½
½
½
½
½
½
½
½
½
½
b
a
Fig. 10 Four unit cells of Te-III at 8.5 GPa, as viewed down the
a
axis. The six nearest-neighbour
contact distances for each atom are shown, and those atoms at the body centres are labelled with
“1/2”. The modulation wave is indicated by the
dotted lines
Once Te-III was identified as incommensurate, subsequent analysis was con-
ducted on the previously-collected powder-diffraction data using the formalism of
4D superspace [
234
], and the JANA2000 software for structure refinement [
235
].
The Rietveld refinement of the incommensurate Te-III diffraction profile is shown
in Fig.
9
, and the modulated structure is shown in Fig.
10
. Tellurium was only the
second element found to have a modulated crystal structure at high-pressure, the
