静高压加载下LY12铝的超声测量与等温状态方程

 利用“脉冲回波重合法”测量了多晶LY12铝在流体静压加载下的纵波与横波声速随压力的变化。并根据较低压力（<0.5 GPa）下的超声测量数据所确定的零压弹性模量及其对压力的偏导数,导出了LY12铝的Murnaghan、Birch-Murnaghan、Vinet三种不同形式的等温状态方程,发现由超声测量数据导出的Vinet 状态方程能很好地描述面心立方（fcc）结构的铝与铝合金在较高压力（约200 GPa）下的压缩特性。此外,由超声数据计算了LY12铝在室温常压条件下的Debye温度为430.97 K、热力学Grüneisen系数为2.025、平均声模Grüneisen系数为2 379。     

纤锌矿氮化硼及其应用的研究（Ⅱ）——纤锌矿型氮化硼的等温状态方程

 使用两种不同的高压在位X光衍射法，研究了用爆炸法合成的纤锌矿型氮化硼（wBN）在室温下的等温状态方程。一种方法是用转靶X光角色散粉末衍射法，研究了它在0~40 GPa压力范围内的等温压缩行为。结果表明，wBN在0~40 GPa的压力范围内是稳定的，没有发生结构相变。通过p-V数据对Murnaghan方程拟合，得到wBN在p=0时的等温体模量B₀=(335±34) GPa及其对压力的一阶导数B₀'=4.21；另一种是用同步辐射X光能量色散衍射法，研究了它在0~25 GPa压力范围内的等温状态方程。实验中，使用了改进的自动加压的DAC高压装置，此装置保证了实验中衍射角θ₀固定不变。将获得的p-V数据仍用Murnaghan方程拟合，得到wBN在p=0时等温体模量B₀=(280±56) GPa，及其B₀'=4.39。     

钠玻璃与钛玻璃在静水压下的弹性性能

用超声脉冲重叠法测量了钠玻璃(float glass)和钛玻璃(SiO₂+8.4wt%TiO₂)从大气压到2GPa静水压条件下的纵波声速和横波声速.发现两种玻璃有不同的变化规律.钛玻璃的纵波声速和横波声速,与钠玻璃的横波声速都随压力的增加而减小;而钠玻璃的纵波声速随压力的增加先增大,后减小.这一现象不同于别的氧化硅玻璃.对实验结果进行了讨论,并计算了弹性模量在压力下的变化和Murnaghan状态方程参数. 关键词： 高压 超声 玻璃     

50 GPa下NiO等温状态方程的高压X光研究

 本文采用在位的（in situ）高压X光衍射方法研究了近50 GPa和室温下三方结构NiO的等温压缩行为，并用Murnaghan状态方程对实验值进行了最小二乘法拟合，得到的NiO室温状态方程的相应参量分别为：B₀=223 GPa，B₀'=4.21。在室温压力范围内没有观察到第一类结构相变。NiO在六方指标下的轴比c/a随压力的变化在实验压力范围内可用c/a=2.450~1.569×10^-3（GPa）近似描述。     

高压下碱卤晶体的状态方程

 从碱卤晶体总相互作用势能出发,得到了一个状态方程。在不存在压致转变的压力范围内,该方程能够很精确地描述室温时碱卤晶体在高压下的等温压缩行为。还进一步讨论了体积弹性模量和其压力导数之间的关系。计算结果与实验结果符合得很好。     

铝的等温状态方程

 采用原位高压同步辐射X射线衍射技术,利用金刚石对顶砧（DAC）装置产生高压,选用高纯NaCl粉末作为传压介质与标压物质,在室温下、21.5 GPa的压力范围内,测定了铝的等温状态方程。利用Murnaghan方程对实验结果进行了数值拟合,得到铝的零压体弹模量及其一级压力导数分别为B₀=(77±2) GPa,B₀′=4.8±0.3。该结果同相关文献资料报导的值在误差范围内符合得很好,略显得较大,这是由于传压介质NaCl的非静水压效应所致。在实验所达到的压力范围内,未发现明显的相变迹象。     

压力下 Nd60Al10Fe20Co10块体金属玻璃的弹性行为

室温下在等静压最高达～0.5GPa的条件下,利用超声回波技术测量了超声波横波和纵波在Nd60Al10Fe20Co10块体金属玻璃中的传播时间来确定横波和纵波速度.测量时所采用的超声波频率为10MHz.利用所测量的数据,建立了超声波波速、样品的密度、弹性模量以及Debye温度等与所施加的压力之间的相互关系.并且推导出Murnaghan状态方程.另外,基于非晶态与晶态物理性能的相似性,对此块体非晶的压缩曲线、弹性常数和Debye温度等进行了理论计算,结果表明Nd60Al10Fe20Co10块体金属玻璃的弹性性能与其组成的元素有着密切的关系.     

高压下天然顽火辉石能量色散X射线粉末衍射研究

 在北京同步辐射装置（BSRF）高压站对采自于河北大麻坪的天然顽火辉石,在室温高压（0~31.64 GPa）下,利用金刚石压腔装置（DAC）,进行了能量色散X射线粉末衍射（EDXD）原位测量,得到了顽火辉石在不同压力下的衍射图谱,并利用UnitCell软件进行解谱,获得了其晶胞参数a、b、c和晶胞体积V及其随压力的变化,最后利用Murnaghan等温方程得到了天然顽火辉石的体积模量K_T(0)=172 GPa、压缩系数及p-V状态方程,发现沿a、b、c三方向的压缩系数存在明显的各向异性,结果与斜方辉石的弹性波速各向异性完全一致。     

压力下Nd60Al10Fe20Co10块体金属玻璃的弹性行为

室温下在等静压最高达～0.5GPa的条件下，利用超声回波技术测量了超声波横波和纵波在Nd₆₀Al₁₀Fe₂₀Co₁₀块体金属玻璃中的传播时间来确定横波和纵波速度.测量时所采用的超声波频率为10MHz.利用所测量的数据，建立了超声波波速、样品的密度、弹性模量以及Debye温度等与所施加的压力之间的相互关系.并且推导出Murnaghan状态方程.另外，基于非晶态与晶态物理性能的相似性，对此块体非晶的压缩曲线、弹性常数和Debye温度等进行了理论计算，结果表明Nd₆₀Al₁₀Fe₂₀Co₁₀块体金属玻璃的弹性性能与其组成的元素有着密切的关系. 关键词： 块体金属玻璃 弹性性能 等静压     

一种易碎玻璃转变温度的研究

利用超声相比较和相位探测法,测量了一种易碎玻璃纵波和横波声速从室温到73℃范围内的变化,由此得到弹性模量随温度的变化规律.发现声速和弹性模量随温度变化曲线的斜率在54℃附近有明显变化,存在一个转变温度点,测是结果与布里渊散射在此温区相应的数据符合.研究表明,这个转变温度是易碎玻璃完全熔化前的玻璃化转变温度,比其它玻璃低得多. 关键词：     

Two universal equations of state for solids satisfying the limiting condition at high pressure

In this paper it is shown that the relationship of bulk modulus with pressure, B=f(P), should be linear both at low and high-pressure limiting conditions. Because most of present equations of state (EOS) for solids cannot satisfy such linear relationship at high pressure, a new function f(P) is proposed to satisfy the linearity. By integrating the bulk modulus, an EOS with three parameters and satisfying the quantum-statistics limitation is derived. It is shown that the EOS can be reduced to two-parameter EOS approximately satisfying the limiting condition. By applying the two EOSs and other three typical EOSs to 50 materials, it is concluded that for materials at low and middle-pressure regimes, the limiting condition does not operate, the Baonza EOS gives the best results, but it cannot provide analytic expression for cohesive energy. The Vinet and our second EOSs are slightly inferior, both EOSs can provide analytic expression for cohesive energy, and for materials at high-pressure regimes our second EOS gives the best results. The Holzapfel and our first EOSs give the worst results, although they strictly satisfy the limiting condition. For practical applications, the limiting condition is not important because it only operates as V→0.     

Simulated equation of state of CaF2 with fluorite-type structure at high temperature and high pressure

The pressure-volume-temperature (P-V-T) equation of state (EOS), isothermal bulk modulus, and thermal expansivity of CaF₂ with cubic fluorite-type structure are investigated using the constant temperature and pressure shell model molecular dynamics (MD) method with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction. It was shown that MD simulation is very successful in accurately reproducing the measured volumes of the CaF₂ over a wide range of pressures. The simulated P-V data matched X-ray diffraction experimental results up to 9.5 GPa at 300 K. In addition, volume thermal-expansion coefficient and isothermal bulk modulus were also calculated and compared with available experimental data and the latest theoretical results at ambient condition. At extended temperature and pressure ranges, The P-V EOS under different isotherms at selected temperatures, T-V EOS under different isobars at selected pressures, thermal expansivity, and isothermal bulk modulus were predicted up to 1500 K and 10 GPa. The detailed knowledge of thermodynamic behavior and EOS at extreme conditions are of fundamental importance to the understanding of the physical properties of CaF₂.     

Analysis of K-prime equations of state

We present an analysis of the $K$-prime equations of state (EOS) due to Keane and Stacey. It is found that the two EOS differ significantly from each other in some important respects. $K$-prime represents the pressure derivative of the bulk modulus. It is shown that the volume dependence of $K$-prime and higher derivative properties predicted from the Keane EOS are compatible with those predicted from Stacey’s reciprocal $K$-prime EOS only when the Murnaghan approximation is valid. It has been emphasized that the Stacey EOS is more appropriate for describing the relationship between pressure and the bulk modulus and its pressure derivative. The results based on the two EOS have been compared and discussed.     

Pressure dependence of crystal structure and molecular packing in anthracene

Anthracene molecular crystal has been investigated up to a pressure of 10.5 GPa at room temperature using variable shape variable size Monte Carlo simulations in an isothermal–isobaric ensemble. We have reported various structural quantities, such as cell parameters and unit cell volume, as a function of pressure and compared them with the experimental results [J. Chem. Phys. 119, 1078 (2003)]. The pressure dependence of angles θ, δ and χ which describe the relative packing of molecules in the crystal has been calculated. We report that anthracene molecular crystal does not exhibit any first order phase transition up to a pressure of 10.5 GPa which is consistent with the experimental observations by Oehzelt et al. [Phys. Rev. B 66, 174104 (2002)]. The calculated equation of state (EOS) has been fitted to a Murnaghan-type EOS with good agreement. The calculated bulk modulus and the pressure derivative of bulk modulus are 8.2 GPa and 8.9 respectively which are in agreement with the experimentally calculated values.     

百吉帕压力下固态氩的状态方程

 利用最新的X光衍射实验数据和Ar原子的弹性散射实验结果，得到了Ar原子间的相互作用和350 GPa下的固态氩的状态方程。这个状态方程可以作为超高压力下的压标。在150 GPa以上的压标，是目前高压研究中急需的。固态氩既可作为准静水压传压介质，又可作为高压X光衍射中的压标使用。本文计算了固态氩的Grüneisen参数、Debye特征参数、定容比热和等温体模量随压力的变化，压力范围为0~150 GPa。     

C60 under pressure-bulk modulus and equation of state

C₆₀ has been investigated under pressure up to 13 GPa using angular dispersive X-ray scattering and a diamond anvil cell. The resolution of the experimental setup allows to examine the volume decrease dV/dp under pressure even for pressures of a tenth of a GPa. The obtained data of numerous experimental runs result in a bulk modulus of 13.4 GPa, which is much smaller than the value reported by Duclos et al. [1]. At 170 K and 70 K a bulk modulus of 14.2 GPa and 14.7 GPa was obtained, respectively. The pressure induced fcc-sc transition at 300 K was clearly visible at approx. 0.3 GPa with a jump in the lattice parameter of 0.05 Å. With increasing pressure we found an extreme change in dV/dp, which disables the usage of common equations of state (EOS), like the Murnaghan [2] or Birch [3] equation. Considering the small compressibility of the fullerence molecules we suggest a modified EOS to describe the experimental data.     

Five-parameter equation of state for solids correctly incorporating cohesive energy data

A five-parameter equation of state (EOS) is proposed to correctly incorporate the cohesive energy data in it without physically incorrect oscillations.The proposed EOS is applied to 10 selected metals.It is shown that the calculated compression curves are in good accordance with the experimental data.The values of the bulk modulus and its derivative with respect to pressure extracted from the proposed EOS remain almost unchanged while the data range used is varied.     

Calculation of thermodynamic properties of Ni nanoclusters via selected equations of state based on molecular dynamics simulations

We present an approach for constant-pressure molecular dynamics simulations. This approach is especially designed for finite systems, for which no periodic boundary condition applies. A molecular dynamics (MD) simulation for Ni nanoclusters is used to calculate their pressure–volume–temperature (p–v–T) data for the temperature range 200 K≤T≤400 K, and pressures up to 600 kbar. Isothermal sets of p–v–T data were generated by the simulation; each set was fitted by three equations of state (EoSs): Linear Isotherm Regularity-II (LIRII), Birch–Murnaghan (BM), and EOS III. It is found that the MD data are satisfactorily reproduced by the EoSs with reasonable precision. Some features of the EoSs criteria, such as the temperature dependences of the coefficients, the isothermal bulk modulus and its pressure derivative at the zero-pressure limit, and isobaric thermal expansion for Ni nanoclusters, are investigated. We have found that same EoSs are valid for both bulk Ni and Ni nanoclusters, but with different values of the parameters, which depend on the cluster size and temperature. An increase in bulk modulus with decrease of cluster size can be observed. Also, an increase in isobaric expansion coefficient with decrease of cluster size has been found.     

Equations of State for Regular Solids

Equations of State (EOS) for solids under strong compression and wide ranges in temperature are most commonly represented by "parametric" EOS forms using temperature dependent parameters for the volume V 0 , the bulk modulus K 0 , and its pressure derivative K_{0}^{\prime} for the given ambient (or zero) pressure. Therefore, various common "parametric" EOS forms are compared at first with the recently proposed [1,2] A dapted P olynomical expansion AP2, and in the second part with the Mie-Grüneisen approach, which uses one of the common EOS forms for the pressure of the static lattice or for the zero temperature isotherm, p ZT ( V ), and a detailed modelling of the additional thermal pressure, p th ( V , T ), in the form p(V,T) = p_{\rm ZT}(V) + p_{\rm th}(V,T) . Thereby, it is shown, that "intrinsic" anharmonicity effects have to be taken into account and between the two schemes differences of the order of a few percent in pressure are noticed for regular solids, like Cu, Ag, and Au. These differences are discussed with respect to the present uncertainties in a practical pressure scale for wide ranges in pressure (up to several TPa) and in temperature (up to 1500 K and above).