部分电离稠密氦等离子体物态方程的自洽变分计算

稠密氦在高温高压下将会发生电离, 电离能会因为原子、离子以及电子之间的相互作用而降低. 考虑He，He⁺，He²⁺，e之间的相互作用, 通过粒子化学势平衡得到非理想的电离平衡方程，用自洽流体变分过程对方程求解, 进而对自由能求导获得体系的热力学状态参量. 模型计算结果与已有的实验和理论计算相一致. 用此模型预测密度10^-3—10^0.3 g/cm³和温度4—7 eV范围的物态方程, 获得了压力在500　GPa以内的理论数据. 计算表明粒子间的非理想相互作用引起的电离能降低是出现压致电离现象的主要原因，在高温高密度物态方程的计算中必须考虑粒子间非理想相互作用对电离能修正的影响. 关键词： 氦 物态方程 部分电离等离子体 自洽变分     

Effects of Shock Pressure on Transition Pressure in Zr

Measurements of free surface velocity profiles of high-purity Zr samples under shock-wave loading are performed to study the dynamic strength and phase transition parameters. The peak pressure of the compression waves is within the range from 9 to 14 GPa, and the Hugoniot elastic limit is 0.5 GPa. An anomalous structure of shock waves is observed due to the α - ω phase transition in Zr. Shock pressure has effects on transition pressure which increases with increasing compression strength, and the stronger shocks have a lower transit time.     

非均匀性对自由面粒子速度信号的影响

在平板撞击实验中,通常利用应力计或VISAR来获得样品中应力历史或自由面粒子速度信号来研究材料的动态力学性能.本文采用含预制缺陷的K9玻璃作为研究对象,利用口径为37mm火炮加载装置,在靶样品的自由面上2 mm线长度范围内,利用16路激光多普勒探针测量系统(DPS),对样品自由面不同位置的自由粒子速度同时进行测量,此方法不同于传统的单点VISAR测量样品自由面速度,其空间分辨率为127μm,可分辨材料内部非均匀性(尺寸大于127μm的夹杂、缺陷等)对自由面速度信号的影响.本文的实验方法可为从细观尺度研究材料动态力学性能提供一种研究思路.     

MoⅩⅣ-PdⅩⅧ离子n=4 Complex谱线和振子强度

用HXR方法计算了MoⅩⅣ -PdⅩⅧ离子n =4Complex(4l,l=s,p ,d ,f)组态能级。通过分析该等电子序列离子能级的实验值与理论值之差ΔE随Zc 变化规律 ,提出了一种新的拟合公式。用该公式和所设计的FORTRAN程序对上述组态各能级的HXR理论计算值进行了系统的拟合计算。获得了上述组态跃迁谱线波长和相应的振子强度     

钽在冲击载荷下的动态力学特性

 在对称碰撞实验中,用VISAR测试系统记录了自由面粒子速度剖面。结合材料常压弹性纵波声速的测量,利用冲击加载的双波结构,测量了钽在30 GPa以内的冲击波速度,给出了线性相关性非常好的D-u_p 关系,并与高压下的测量结果作了比较。同时对由自由面粒子速度剖面来计算层裂强度的模型进行了讨论,发现模型差异对钽的层裂强度的影响超过30%。     

Structural and thermodynamic properties of wurtzite-type aluminium nitride from first-principles calculations

The lattice parameter, bulk modulus and its pressure derivative of the wurtzite-type aluminium nitride (w-AlN) are investigated by using the Cambridge Serial Total Energy Package (CASTEP) program in the framework of Density Functional Theory (DFT). The calculated results are in good agreement with the available experimental data and other theoretical results. Through the quasi-harmonic Debye model, the dependences of the normalized lattice parameters $a/a_{0}$ and $ c/c_{0}$, axial ratio $c/a$, normalized primitive-cell volume $V/V_{0}$, Debye temperature ${\it\Theta} _{\rm D} $ and heat capacity $C_{\rm V}$ on pressure $P $ and temperature $ T$ are obtained. It is found that the interlayer covalent interactions (Al-N bonds) are more (even a little) sensitive to temperature and pressure than intralayer ones (N--N bonds), which gives rise to a little lattice anisotropy in the w-AlN.     

Thermoelasticity of CaO from first principles

The thermoelastic properties of CaO over a wide range of pressure and temperature are studied using density functional theory in the generalized gradient approximation. The transition pressure taken from the enthalpy calculations is 66.7GPa for CaO, which accords with the experimental result very well. The athermal elastic moduli of the two phases of CaO are calculated as a function of pressure up to 200GPa. The calculated results are in excellent agreement with existing experimental data at ambient pressure and compared favourably with other pseudopotential predictions over the pressure regime studied. It is also found that the degree of the anisotropy rapidly decreases with pressure increasing in the B1 phase, whereas it strongly increases as the pressure increases in the B2 phase. The thermodynamic properties of the B1 phase of CaO are predicted using the quasi-harmonic Debye model; the heat capacity and entropy are consistent with other previous results at zero pressure.     

Melting and Grüneisen parameters of NaCl at high pressure

The Buckingham potential has been employed to simulate the melting and thermodynamic parameters of sodium chloride (NaCl) using the molecular dynamics (MD) method. The constant-volume heat capacity and Grüneisen parameters have been obtained in a wide range of temperatures. The calculated thermodynamic parameters are found to be in good agreement with the available experimental data. The NaCl melting simulations appear to validate the interpretation of superheating of the solid in the one-phase MD simulations. The melting curve of NaCl is compared with the experiments and other calculations at pressure 0－30GPa range.     

固氪物态方程的关联量子化学计算

运用多体展开理论和量子化学方法—–超分子单、双(三重)激发微扰处理耦合簇CCSD(T)方法,首次系统地计算了面心立方固氪在较宽(从晶格平衡位置到体积压缩率超过3倍)区间的两体、三体和四体相互作用对结合能和物态方程的贡献大小,包括Hartree-Fock自洽场项和范德瓦耳斯长程关联作用项;并与实验数据进行比较.结果表明,在考虑到两体、三体、四体相互作用能后,多体展开理论以及CCSD(T)方法对平衡位置结合能测量数据0—130 GPa整个研究区间的实验物态方程数据都做出令人满意的描述.     

类镓等电子序列PdⅩⅥ－TeⅩⅫ的4s~24p－4s4p~2、4s~24p－4s~25s跃迁谱线和振子强度的理论计算

对类镓等电子序列ＧａⅠ－ＸｅⅩⅩⅣ离子４ｓ２４ｐ、４ｓ４ｐ２、４ｓ２、５ｓ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ＳｕⅩⅩ－ＴｅⅩⅫ离子４ｓ２４ｐ、４ｓ４ｐ２、４ｓ２５ｓ组态能级，并给出４ｓ２４ｐ－４ｓ４ｐ２、４ｓ２４ｐ－４ｓ２５Ｓ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。