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Free keywords:
SeO2; new phase; high pressure and high temperature
Abstract:
We have investigated SeO2 at high pressures and high temperatures. Two
new phases (beta-SeO2 and gamma-SeO2) and the boundary separating them
have been found, following experimental runs performed at pressures tip
to 15 GPa and temperatures up to 820degreesC. The two phases
crystallize in the orthorhombic system in space group Pmc2(1) (no. 26)
with a = 5.0722(1) Angstrom, b = 4.4704(1) Angstrom, c = 7.5309(2)
Angstrom, V = 170.760(9) Angstrom(3) and Z = 4 for the beta-phase, and
with a = 5.0710(2) Angstrom, b = 4.4832(2) Angstrom, c = 14.9672(6)
Angstrom, V = 340.27(3) Angstrom(3) and Z = 8 for the gamma-phase. Both
phases are stable at ambient pressure and temperature below
-30degreesC. At ambient temperature the phases return to the starting
phase (alpha-SeO2) in a few days. We discuss our findings in relation
to a previous report of in-situ measurements at high pressures and
ambient temperature. (C) 2004 Elsevier Inc. All rights reserved.
