arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2001.05300cond-mat.mtrl-sciphysics.plasm-ph
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高温高压下氧化镁的第一性原理模拟研究

Magnesium Oxide at Extreme Temperatures and Pressures Studied with First-Principles Simulations

François Soubiran, Felipe González-Cataldo, Kevin P. Driver, Shuai Zhang, Burkhard Militzer

摘要:

我们结合两种第一性原理的计算机模拟技术,路径积分Monte-Carlo和密度泛函理论分子动力学,确定了氧化镁在密度为0.35 ~ 71~ gPDMATHABMM cm $^{-3}$,温度为10,000 K ~ $5\times10^8$ ~K的温密物质状态方程。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MgO的电子结构和电离机制作为密度和温度的函数。我们发现,镁和氧的L-壳层轨道杂化在高密度。这导致随着密度和温度的增加,L壳层逐渐电离。在这方面,MgO的行为与纯氧不同,这反映在MgO主震Hugoniot曲线的形状上。氧的曲线显示两个压缩最大值,而MgO的曲线仅显示一个。我们预测在温度为6.73 $\times 10^7$ K时,最大压缩比为4.66。最后,我们研究如何多重冲击和斜坡波可以用来覆盖一个大的密度和温度范围。

英文摘要:

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$^{-3}$ and temperatures from 10,000 K to $5\times10^8$~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 into 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 $\times 10^7$ K. Finally we study how multiple shocks and ramp waves can be used to cover a large range of densities and temperatures.

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