Department of Earth and Planetary Science, University of California, Berkeley, USA.
J Phys Condens Matter. 2013 Oct 16;25(41):415401. doi: 10.1088/0953-8984/25/41/415401. Epub 2013 Sep 11.
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.
我们使用电阻加热金刚石压腔中的 X 射线衍射来扩展 AuGa2 的熔化曲线，使其超出 5.5 GPa 和 720 K 的最小值，并限制立方（萤石结构）、正交（钙钛矿结构）和单斜相之间的高温相界。我们记录了克拉珀龙斜率的大幅变化，这与从立方相向低对称相的转变相吻合，表明结构转变是斜率变化的直接原因。此外，在熔化和凝固之间检测到中等（~30 K）到较大（90 K）的滞后，由此我们推断，在高压下，AuGa2 晶体可以在热力学熔化温度以上超过 5%的亚稳状态下存在。
