The metal–nonmetal transition is of fundamental interest in contemporary physics. We present a combination of the optical reflectivity measurement of an expanded gold fluid produced by gold L-band x-rays from a Hohlraum and the corresponding ab initio calculations to study the metal–nonmetal transition. The averaged density and temperature of the reflective layer are derived from 1D radiation hydrodynamic simulations constrained by matching the expansion velocity obtained from the fringe shift. A sharp change in time-resolved reflectivity occurs at one third of the initial density, near where the metal–nonmetal transition is predicted to occur. The reflectivity calculated based on the Helmholtz equations with the dielectric function from the density functional theory calculations is compared with the experimental measurement. Disagreement of reflectivity between calculation and measurement probably originates from the energy shift of the dielectric function due to the inaccurate Kohn–Sham eigenvalue. More accurate methods on calculating the dielectric function are still needed to improve the calculated reflectivity.

中文翻译：

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结合光反射率测量和金属-非金属过渡状态下膨胀金流体的从头算

金属到非金属的转变是当代物理学的基本兴趣。我们介绍了由Hohlraum的金L带x射线和相应的从头算产生的膨胀金液的光学反射率测量的组合计算以研究金属-非金属过渡。反射层的平均密度和温度是通过一维辐射流体动力学模拟得出的，该流体动力学模拟通过匹配从条纹位移获得的膨胀速度而受到约束。时间分辨反射率的急剧变化发生在初始密度的三分之一处，接近预计发生金属-非金属跃迁的位置。将基于Helmholtz方程和介电函数的密度函数理论计算得出的反射率与实验测量值进行比较。计算和测量之间的反射率不一致可能是由于Kohn-Sham特征值不正确而引起的介电函数的能量偏移。