Department of Earth and Planetary Science, University of California, Berkeley, California 94720, USA.
J Chem Phys. 2019 Dec 7;151(21):214104. doi: 10.1063/1.5126624.
We combine two first-principles computer simulation techniques, path integral Monte Carlo and density functional theory molecular dynamics, to determine the equation of state of magnesium oxide in the regime of warm dense matter, with densities ranging from 0.35 to 71 g cm and temperatures ranging from 10 000 K to 5 × 10 K. These conditions are relevant for the interiors of giant planets and stars as well as for shock wave compression measurements and inertial confinement fusion experiments. We study the electronic structure of MgO and the ionization mechanisms as a function of density and temperature. We show that the L-shell orbitals of magnesium and oxygen hybridize at high density. This results in a gradual ionization of the L-shell with increasing density and temperature. In this regard, MgO behaves differently from pure oxygen, which is reflected in the shape of the MgO principal shock Hugoniot curve. The curve of oxygen shows two compression maxima, while that of MgO shows only one. We predict a maximum compression ratio of 4.66 to occur for a temperature of 6.73 × 10 K. Finally, we study how multiple shocks and ramp waves can be used to cover a large range of densities and temperatures.
我们结合了两种第一性原理计算机模拟技术，路径积分蒙特卡罗和密度泛函理论分子动力学，以确定氧化镁在温暖致密物质状态下的状态方程，密度范围从 0.35 到 71 g/cm，温度范围从 10 000 K 到 5 × 10 K。这些条件与巨行星和恒星的内部以及冲击波压缩测量和惯性约束聚变实验有关。我们研究了氧化镁的电子结构和电离机制作为密度和温度的函数。我们表明，镁和氧的 L 壳层轨道在高密度下发生杂化。这导致 L 壳层随着密度和温度的增加而逐渐电离。在这方面，氧化镁的行为与纯氧不同，这反映在氧化镁主激波 Hugoniot 曲线的形状上。氧的曲线显示出两个压缩最大值，而氧化镁的曲线仅显示一个。我们预测在温度为 6.73 × 10 K 时会发生最大压缩比为 4.66 的情况。最后，我们研究了如何使用多个冲击波和斜坡波来覆盖较大的密度和温度范围。
