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.
Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of Low Energy Electron Diffraction
Large Scale Structure Prediction of Near-Stoichiometric Magnesium Oxide Based on a Machine-Learned Interatomic Potential: Novel Crystalline Phases and Oxygen-Vacancy Ordering
利用快速准确的神经网络势,我们能够用最小跳跃方法系统地探索大块氧化镁的大晶胞的能量景观。该潜力的训练重点是近化学计量组成,特别是低氧化物,即,Mg $_x$ O $_{1-x}$与$0.50<x<0.60$。我们广泛的探索表明,对于散装化学计量的化合物,有几个新的低能量岩盐状结构,其中Mg原子是八面体六配位的,并形成具有不同堆叠顺序的三角棱柱图案。此外,对于$x$的每种组成,我们发现了Mg $_x$ O $_{1-x}$的新型非化学计量晶相的密集光谱。这些结构大多类似于具有八面体配位和五配位Mg原子的岩盐结构。由于去除了一个氧原子,能量景观变得更像玻璃,具有氧空位型结构,它们在能量上彼此非常接近。对于相同数量的镁和氧原子,如果空位沿着线或平面排列,则我们的缺氧结构的能量低于具有随机分布的氧空位的岩盐结构。我们还发现了假定的全球最低配置的非化学计量的低氧化物结构的每个组合物。这些结构主要由岩盐结构的(111)板片组成,其在顶部和底部用Mg原子终止,并且沿着$z$方向以不同的顺序堆叠。与其他Magnéli型相一样,这些结构具有与其化学计量对应物显著不同的性质,例如低晶格热导率和高电导率。
Chemical transformation of MgH2/V2O5 composite to Mg-V-O rock salt and its influence on the electrochemical Li conversion and hydrogen storage characteristics of MgH2
University of Aveiro(阿威罗大学);LASI - Intelligent Systems Associate Laboratory(智能系统联合实验室);International Iberian Nanotechnology Laboratory (INL)(伊比利亚纳米技术国际实验室)
Nanocrystalline structure and strain in magnesium under extreme dynamic compression
M.N. Miheev Institute of Metal Physics, Ural Branch, Russian Academy of Sciences(俄罗斯科学院乌拉尔分校 M.N. 米赫耶夫金属物理研究所);NANOTECH Centre, Ural Federal University(乌拉尔联邦大学 NANOTECH 中心)
Epitaxy of Fe3O4 on Si(001) by pulsed laser deposition using a TiN/MgO buffer layer
氧化物材料在硅(Si)衬底上的外延对于使用氧化物的各种物理性质如铁电性、铁磁性或超导性的未来功能器件具有极大的兴趣。最近,具有高自旋极化的载流子的材料已经成为自旋电子学中的氧化物-氧化物混合器件的关注点。在这里,我们报告的脉冲激光沉积磁铁矿(Fe 3 O 4)在Si(001)衬底上清洁的原位激光束高温处理。在沉积氮化钛(TiN)和氧化镁(MgO)的双缓冲层之后,可以生长高质量的外延磁铁矿层,如通过RHEED强度振荡和高分辨率X射线衍射所验证的。
Extreme high-pressure distortion phase of Bi2MoO6 in Bi2Mo0.94W0.06O6 at ambient pressure for augmented octahedral rotations and metal-oxide charge transport
Band convergence and linearization error correction of all-electron GW calculations: The extreme case of zinc oxide
最近,Shih等人[Phys. Rev. Lett. 105,146401(2010)]公开了用非自洽GW近似计算的纤锌矿ZnO的理论带隙,其与实验惊人地一致,同时强烈偏离先前的研究。他们表明,需要大量的空带来收敛间隙。我们重新检查GW计算与全电位线性增强平面波方法,发现即使有3000带的带隙是不完全收敛。双曲线拟合用于外推到无限频带。此外,我们消除了线性化误差的高lying态与本地轨道。事实上,我们计算的带隙比以前的研究大得多,但比Shih等人的要小。
Irradiation-induced amplification of electric fields at oxide interfaces as revealed by correlative DPC-STEM and DFT
Los Alamos National Laboratory(洛斯阿拉莫斯国家实验室);University of California Berkeley(加州大学伯克利分校);Lehigh University(利哈伊大学);Pacific Northwest National Laboratory(太平洋西北国家实验室);Lawrence Berkeley National Laboratory(劳伦斯伯克利国家实验室)
Extreme mixing enables broadband high-temperature electromagnetic absorption in high-entropy perovskites
School of Materials Science and Engineering, South China University of Technology(华南理工大学材料科学与工程学院);College of Integrated Circuits and Optoelectronic Chips, Shenzhen Technology University(深圳技术大学集成电路与光电芯片学院)
Thermodynamically-consistent derivation and computation of twinning and fracture in brittle materials by means of phase-field approaches in the finite element method
From Chemical Complexity to Tunable Magnetic Ordering in Highly Disordered High-Entropy Spinel Oxides
Thapar Institute of Engineering and Technology(塔帕尔工程技术学院);UGC-DAE Consortium for Scientific Research(UGC-DAE科学研究联盟);Freie Universität Berlin(柏林自由大学);Helmholtz Zentrum Berlin für Materialien und Energie(柏林亥姆霍兹材料与能源中心);Normandie University(诺曼底大学)