Geballe ZM, Raju SV, Godwal BK, Jeanloz R. Clapeyron slope reversal in the melting curve of AuGa2 at 5.5 GPa.
JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013;
25:415401. [PMID:
24025237 DOI:
10.1088/0953-8984/25/41/415401]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We use x-ray diffraction in a resistively heated diamond anvil cell to extend the melting curve of AuGa2 beyond its minimum at 5.5 GPa and 720 K, and to constrain the high-temperature phase boundaries between cubic (fluorite structure), orthorhombic (cottunite structure) and monoclinic phases. We document a large change in Clapeyron slope that coincides with the transitions from cubic to lower symmetry phases, showing that a structural transition is the direct cause of the change in slope. In addition, moderate (~30 K) to large (90 K) hysteresis is detected between melting and freezing, from which we infer that at high pressures, AuGa2 crystals can remain in a metastable state at more than 5% above the thermodynamic melting temperature.
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