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OLGA DEGTYAREVA1,
EUGENE GREGORYANZ1,
MADDURY SOMAYAZULU2,
PRZEMYSLAW DERA1,
HO-KWANG MAO1 and
RUSSELL J. HEMLEY1
1 Geophysical
Laboratory, Carnegie Institution of Washington, 5251
Broad Branch Road NW, Washington, District of Columbia
20015, USA
2 HPCAT, Carnegie Institution of Washington,
APS, 9700 South Cass Avenue, Argonne, Illinois 60439,
USA
Correspondence to:
OLGA DEGTYAREVA o.degtyareva@gl.ciw.edu
Nature Materials
AOP Published online: 23
January 2005 | doi:10.1038/nmat1294 |
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Recent developments in high-pressure methods and
advances in X-ray crystallography have led to a new
level of understanding of phase diagrams and structures
of materials under pressure. Recently discovered
phenomena such as complex phases of alkali metals,
incommensurate host−guest structures, and
incommensurately modulated structures have rendered
obsolete our conventional wisdom about the range of
structures possible in the elements. Using new in situ
diffraction techniques, we have resolved the
long-standing problem of the phase-transition sequence
of sulphur in its non-metallic state. We demonstrate
that it is very different from that previously proposed,
with only two phases stable between 1.5 GPa and 83 GPa
(the pressure of metallization), and temperatures from
300 K to 1,100 K. The phases have a triangular chain and
a squared chain structure. The same squared chain
structure is found in the heavier group VI element
selenium. |
