体心立方金的冲击压缩下的测量和熔化。

Measurement of Body-Centered Cubic Gold and Melting under Shock Compression.

机构信息

Lawrence Livermore National Laboratory, Livermore, California 94500, USA.

Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA.

出版信息

Phys Rev Lett. 2019 Jul 26;123(4):045701. doi: 10.1103/PhysRevLett.123.045701.

DOI:10.1103/PhysRevLett.123.045701

PMID:31491279

Abstract

We combined laser shock compression with in situ x-ray diffraction to probe the crystallographic state of gold (Au) on its principal shock Hugoniot. Au has long been recognized as an important calibration standard in diamond anvil cell experiments due to the stability of its face-centered cubic (fcc) structure to extremely high pressures (P >600 GPa at 300 K). This is in contrast to density functional theory and first principles calculations of the high-pressure phases of Au that predict a variety of fcc-like structures with different stacking arrangements at intermediate pressures. In this Letter, we probe high-pressure and high-temperature conditions on the shock Hugoniot and observe fcc Au at 169 GPa and the first evidence of body-centered cubic (bcc) Au at 223 GPa. Upon further compression, the bcc phase is observed in coexistence with liquid scattering as the Hugoniot crosses the Au melt curve before 322 GPa. The results suggest a triple point on the Au phase diagram that lies very close to the principal shock Hugoniot near ∼220 GPa.

摘要

我们将激光冲击压缩与原位 X 射线衍射相结合，在金（Au）的主冲击 Hugoniot 上探测其晶体状态。由于其面心立方（fcc）结构在极高压力（300 K 时超过 600 GPa）下的稳定性，Au 长期以来一直被认为是金刚石压腔实验中的重要校准标准。这与 Au 的高压相的密度泛函理论和第一性原理计算形成鲜明对比，后者预测在中间压力下存在各种具有不同堆积排列的 fcc 类似结构。在这封信中，我们在冲击 Hugoniot 上探测了高压和高温条件，并在 169 GPa 处观察到了 fcc Au，在 223 GPa 处首次观察到了体心立方（bcc）Au。进一步压缩时，bcc 相在穿过 Au 熔体曲线之前与液体散射共存，当 Hugoniot 在 322 GPa 之前越过 Au 熔体曲线时，bcc 相出现。结果表明，Au 相图上存在一个三相点，该点非常接近约 220 GPa 附近的主冲击 Hugoniot。