Structures and Equation of State of ε-Fe under High Pressure

The equation of state （EOS） and the axial ratio c/a of ε-Fe at high pressures are investigated by using the gen- eralized gradient approximation （GGA） within the plane-wave pseudopotential density functional theory （DFT）. The results show that at the lower pressure, the EOS of ferromagnetic ε-Fe is consistent with the experimental result. While at higher pressure, the EOS of the nonmagnetic ε-Fe is in good agreement with the experimental result. Meanwhile, we find an obvious increase of the axial ratio c/a with pressure, and there is only a small increase with increasing temperature at high pressure.     

稠密氘气物态方程研究

 用二级轻气炮作为加载手段,通过瞬态辐射高温计对样品氘的冲击压缩层的光谱辐射亮度历史进行测量,测得氘气中冲击波速度和冲击温度,并用离解电离平衡方程从理论上分析了冲击压缩下稠密气体的组分,理论计算的Hugoniot曲线及冲击温度和实验结果吻合。     

液氢、液氘冲击压缩特性的理论计算

用液体微扰变分理论,计算了液氢,液氘冲击压缩曲线-计算结果与Nellis实验相一致-计算所得冲击温度比Holmes的实验值明显偏高-对冲击压缩曲线与实验一致,以及冲击温度的计算值明显偏高于实验结果的原因进行了分析- 关键词：     

Electrical Resistivity of Silane Multiply Shock-Compressed to 106 GPa

Since Wigner et al. proposed that hydrogen would become metallic under sufficient pressure compres- sions in 1935,scientists have paid their attention on making metallic hydrogen at high pressures, and con- siderable progresses were made in theoretical and ex- perimental researches. Nellis et al. observed that the electrical resistivity of fluid hydrogen declined by several orders of magnitude when liquid hydrogen was multiply shocked to 140 GPa, and concluded that fluid hydrogen underwent metallization phase tran- sition from semiconductor to metal in their experi- ments. Although further researches should be carried out to distinguish the highly conductive state and the metallic state of fluid hydrogen, researchers have made great efforts to find new technical approaches to de- crease the threshold pressure for hydrogen metalliza- tion. For this purpose, hydrogen-rich compounds at- tract much attention. Some researchers believed that non-hydrogen elements in those compounds may re- duce, to some extent, the activation energy of met- allization by the effect of chemical pre-compression. Silane, a typical hydrogen-rich compound of group IV hydrides, has been the subject of most of the theoretical and experimental research so far, and it was also expected to be a potential candidate for a high-To superconductor at high pressure research.[61 Compared to hydrocarbons,[71 the chemical bonds in the silane molecule are theoretically more sensitive to pressure and temperature. At sufficiently high pres- sure and temperature, the fluid silane possibly be- comes some metallic alloy consisting of hydrogen and silicon elements. Theoretical calculations showed thatthe metallic transition for the silane system may oc- cur even below 100 GPa, while there are also some other later articles that claimed that silane would re- main an insulator up to around 200 GPa and became metallic and supconducting at 220 GPa with a theo- retical Tc of 16 K. Recently, Eremets et al. have re- ported that silane can transform to metal at 50 GPa,     

类镓等电子序列PdⅩⅥ—TeⅩⅫ的4s^24p—4s4p^2,4s^24p—…

对类镓等电子序列ＧａⅠ－ＸｅⅩⅪⅤ离子４ｓ＾２４ｐ，４ｓ４ｐ＾２，４ｓ＾２５ｓ组态能级结构和组态相互作用进行了理论分析，找出沿等电子序列的变化规律。用我们提出的拟合公式预测ＳｎⅩⅩ－ＴｅⅩⅫ离子４ｓ＾２４ｐ，４ｓ４ｐ＾２，４ｓ＾２５ｓ组态能级，并给出４ｓ＾２４ｐ－４ｓ４ｐ＾２，４ｓ＾２４ｐ－４ｓ＾２５ｓ谱线波长和ＨＸＲ方法的理论计算振子强度，理论计算值与实验值进行了比较。     

类镓等电子序列ZrⅩ-RhⅩⅤ离子的4s~24p-4s~24d、4s~24p-4s4p~2、4s~24p-4s~25s、4p~3-4s~25s以及4s4p~2-4p~3跃迁谱线和振子强度的理论计算

本文对类镓等电子序列ＧａⅠ—ＸｅⅩⅩⅠⅤ离子４ｓ２４ｐ、４ｓ２４ｄ、４ｓ４ｐ２、４ｐ３和４ｓ２５ｓ组态能级结构和组态相互作用进行了理论分析，找出沿等电子序列的变化规律。用作者提出的半经验公式［１］，内插预测了ＴｃⅩⅢ离子的４ｓ２４ｐ、４ｓ４ｐ２和４ｓ２５ｓ组态能级，外推预测了ＴｃⅩⅢ—ＲｈⅩⅤ离子的４ｐ３和４ｓ２４ｄ组态能级，并给出了４ｓ２４ｐ４ｓ２４ｄ、４ｓ２４ｐ４ｓ４ｐ２、４ｓ２４ｐ４ｓ２５ｓ、４ｐ３４ｓ２５ｓ和４ｓ４ｐ２—４ｐ３谱线波长和ＨＸＲ方法理论计算振子强度。用作者提出的半经验公式对组态能级的预测值与实验值的最大偏差小于１００ｃｍ－１。     

Simulation of Ab Initio Molecular Dynamics of Shock Wave on Copper

The relation between particle velocity Up, up to 4 km/s, and shock wave velocity Us in copper has been simulated with ab initio molecular dynamics. The simulated relationship without considering the correction of zero-point and finite temperature effects is Us = 4.23 1.53Up. After considering the correction the relation becomes Us = 4.08 1.53Up, which is consistent with the experimental result.     

高密度流体He+H2混合物物态方程研究

选择高密度流体He H2混合物作为研究对象，用Ree混合规则和van der Waals单组分流体变分微扰理论加量子力学一级修正模型编制计算程序。作为对计算模型及其程序的检验，首先用已有的α-exp-6优化势参数，计算了T=300K的He H2混合物的等温相平衡线，得到了与实验值和分子动力学(MD)数值模拟一致的结果，然后进一步计算了0～60GPa和50～7000K压力温度范围内的流体He H2混合物(He H2分别为1：1、1：3、3：1摩尔比)的高压物态方程。与Monte-Carlo模拟数据所进行的比较表明，在低温下，量子力学修正对热力学量的计算是重要的。     

高温高压下钼的结构稳定性研究

以钼为代表的一系列过渡金属,在高温高压的相变及结构稳定性研究是实验和理论研究的热点.钼在常温常压下是bcc结构,但是在高温高压下可能的相结构一直未能确定.本文首先预测了几种高压下的结构,并计算了其自由能及力学性质.针对可能的hcp结构,我们通过新近发展的自洽晶格动力学方法,充分考虑声子间相互作用,成功获得了hcp结构高温高压声子色散曲线,结果表明hcp相在热力学及动力学上都是能够稳定存在的结构,是一种可能的高压相.     

四体相互作用对固氦压缩特性的贡献

运用从头计算自洽场方法和原子团簇理论计算了高压下固氦原子间的四体势分量.计算结果表明四体分量对结合能的贡献为正；随着压缩度增大四体势的贡献比例变大.采用两体、三体、四体势和Aziz吸引势计算固氦零温状态方程并与实验测量相比较，结果表明两体势对固氦的压缩性贡献了过多的正效应，加入三体分量的修正，仅在低于10GPa时理论值与实验值相符很好，但考虑了四体势修正后能将理论值与实验值符合程度提高到 27GPa. 关键词： 状态方程 固氦 四体势 从头计算