The solid inner core of the Earth is predominantly composed of iron alloyed with several percent Ni and some lighter elements, Si, S, O, H, and C being the prime candidates. There have been a growing number of papers investigating C and H as possible light elements in the core, but the results are contradictory. Here, using ab initio simulations, we study the Fe-C and Fe-H systems at inner core pressures (330-364 GPa). Using the evolutionary structure prediction algorithm USPEX, we have determined the lowest-enthalpy structures of possible carbides (FeC, Fe2C, Fe3C, Fe4C, FeC2, FeC3, FeC4 and Fe7C3) and hydrides (Fe4H, Fe3H, Fe2H, FeH, FeH2, FeH3, FeH4) and have found that Fe2C (Pnma) is the most stable iron carbide at pressures of the inner core, while FeH, FeH3 and FeH4 are stable iron hydrides at these conditions. For Fe3C, the cementite structure (Pnma) and the Cmcm structure recently found by random sampling are less stable than the I-4 and C2/m structures found here. We found that FeH3 and FeH4 adopt chemically interesting thermodynamically stable structures, in both compounds containing trivalent iron. The density of the inner core can be matched with a reasonable concentration of carbon, 11-15 mol.percent (2.6-3.7 wt.percent) at relevant pressures and temperatures. This concentration matches that in CI carbonaceous chondrites and corresponds to the average atomic mass in the range 49.3-51.0, in close agreement with inferences from the Birch's law for the inner core. Similarly made estimates for the maximum hydrogen content are unrealistically high, 17-22 mol.percent (0.4-0.5 wt.percent), which corresponds to the average atomic mass in the range 43.8-46.5. We conclude that carbon is a better candidate light alloying element than hydrogen.
Iron under Earth's core conditions: Liquid-state thermodynamics and high-pressure melting curve
基于密度泛函理论的{ \em Ab initio}方法在投影增广波的实现下被用来计算与地核相关的高压高温下液态铁的自由能和一系列其他热力学性质。{ \em ab initio}自由能通过使用热力学积分计算从简单参考系到{ \em ab initio}系统的自由能变化而获得，热平均值通过{ \em ab initio}分子动力学模拟计算。参考系由以前工作中使用的反幂对势模型组成。将液态自由能与先前使用相同的{ \em ab initio}技术计算的六方密堆积Fe的自由能相结合，以获得熔化曲线和熔化的体积和熵。计算的熔化性能与实验测量和其他最近的{ \em从头计算}预测的比较。实验理论的比较，也提出了固体和液体Hugoniot曲线交叉的熔化线的压力，以及声速和Grüneisen参数沿Hugoniot。根据实验数据，与常用的高压/高温Fe的状态方程进行了额外的比较。
Ab initio melting temperatures of bcc and hcp iron under the Earth's inner core condition
关于地球内核条件下铁的稳定相存在着长期的争论。由于内核边界处的固液共存，固相的热力学稳定性与其熔化温度直接相关，这仍然存在很大的不确定性。在本研究中，我们利用一个半经验势拟合到高温从头算数据进行热力学积分从经典系统描述的潜力从头算系统。该方法为热力学积分提供了一条平滑的路径，并显著降低了有限尺寸效应引起的不确定性。结果表明，在铁的内核条件下，hcp相是纯铁的稳定相，而在熔化温度附近，hcp相和bcc相的自由能差很小，约为10 s meV/atom.
Stabilization of carbon nanotubes by filling with inner tubes: An optical spectroscopy study on double-walled carbon nanotubes under hydrostatic pressure
Stable compounds in the CaO-Al2O3 system at high pressures
利用进化晶体结构预测算法USPEX，我们表明，在地球下地幔的压力CaAl 2 O 4是唯一稳定的铝酸钙。在7.0 GPa以上的压力下，它具有CaFe 2 O 4型结构和空间群Pnma。该相是地球下地幔中主要的候选铝质相之一。结果表明，在低压下，空间群为Cmc 21的5CaO * 3Al 2 O3（C5 A3）、CaAl 4 O 7（C2/c）和CaAl 2 O 4（P21/m）结构分别在2.1、1.8和7.0GPa的压力下是稳定的。从我们的计算中还发现了以前未知的正交'CA-III'相的结构。该相是亚稳态的，具有空间群为P21212的层状结构。
Pohang University of Science and Technology（韩国科学技术院）；Center for High Pressure Science and Technology Advanced Research (HPSTAR)（高压科学和技术先进研究中心）；Institute of Geochemistry, Chinese Academy of Sciences（中国科学院地球化学研究所）
Comparative high-pressure study on rare-earth entropy fluorite-type oxides
Universitat de Valencia（瓦伦西亚大学）；Institut de Ciència dels Materials de la Universitat de València（瓦伦西亚大学材料科学研究所）；University of Zagreb（萨格勒布大学）；Diamond Light Source Ltd.（钻石光源有限公司）；CELLS-ALBA Synchrotron Light Facility（CELLS-ALBA同步辐射光源设施）
Mimicking the earth core conditions with ultrafast laser materials interaction
The Ohio State University（俄亥俄州立大学）；CNRS, Institut d’Optique Grduate School, Laboratoire Hubert Curien UMR 5516, Université Jean Monnet（法国国家科学研究中心，光学研究生院，居里安实验室，圣艾蒂安大学）；Center for Electron Microscopy and Analysis（电子显微镜与分析中心）；Colorado State University（科罗拉多州立大学）；XUV Lasers Inc（XUV激光公司）
