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Atomic ordering in cubic bismuth telluride alloy phases at high pressure
DOI:
10.1103/PhysRevB.93.224109
Authors:
I.
Loa
(University of Edinburgh)
,
J.-w.
Bos
(Heriot-Watt University)
,
R. A.
Downie
(Heriot-Watt University)
,
K.
Syassen
(Max-Planck-Institut für Festkörperforschung)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Physical Review B
, VOL 93
State:
Published (Approved)
Published:
June 2016
Diamond Proposal Number(s):
8105
Abstract: Pressure-induced transitions from ordered intermetallic phases to substitutional alloys to semi-ordered phases were studied in a series of bismuth tellurides. By using angle-dispersive x-ray diffraction, the compounds Bi 4 Te 5 , BiTe, and Bi 2 Te were observed to form alloys with the disordered body-centered cubic (bcc) crystal structure upon compression to above 14–19 GPa at room temperature. The BiTe and Bi 2 Te alloys and the previously discovered high-pressure alloys of Bi 2 Te 3 and Bi 4 Te 3 were all found to show atomic ordering after gentle annealing at very moderate temperatures of ∼100 ∘ C . Upon annealing, BiTe transforms from bcc to the B2 (CsCl) crystal-structure type, and the other phases adopt semi-disordered variants thereof, featuring substitutional disorder on one of the two crystallographic sites. The transition pressures and atomic volumes of the alloy phases show systematic variations across the Bi m Te n series including the end members Bi and Te. First-principles calculations were performed to characterize the electronic structure and chemical bonding properties of B2-type BiTe and to identify the driving forces of the ordering transition. The calculated Fermi surface of B2-type BiTe has an intricate structure and is predicted to undergo three topological changes between 20 and 60 GPa.
Subject Areas:
Materials
Instruments:
I15-Extreme Conditions
Other Facilities: ESRF
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