共查询到20条相似文献,搜索用时 31 毫秒
1.
The generalized Grüneisen parameters (γ′
j
) and (γ″
j
) for cadmium and zirconium were calculated from the second- and third-order elastic constants to determine the low temperature
limit of the volume thermal expansion of these metals of hexagonal symmetry. The low temperature limit of cadmium and zirconium
was calculated to be positive values indicating a positive volume expansion down to 0 K even though many Grüneisen gammas
were found to be negative. 相似文献
2.
基于Gray金属三相状态方程模型,分别采用ργ=常数,Gray,GRIZZLY的Grüneisen系数模型和从头算给出的Grüneisen系数,系统计算了铝的熔化曲线、等熵压缩线、等温压缩线和等熵卸载线,计算结果与实验数据比较表明;在冲击压力约为500GPa的宽广压力范围,GRIZZLY Grüneisen系数模型是最适合描述铝的热力学特性的形式,ργ=常数模型次之,在高压区,Gray和从头算的Grüneisen系数的计算结果与实验值差距较大.
关键词:
Grneisen系数
状态方程
铝 相似文献
3.
4.
Abstract “Regular” linear relations between shock and particle velocities, us = us0, + c · up, imply a divergence of the Hugoniot pressure pH at a critical compression V c/V o = (c-1)/c, where the thermal pressure Δp th = (γ/V)· ΔU th = p H-p T becomes very large with respect to the cold (isothermal) pressure p T at this compression. The Hugoniot relation for the total internal energy U H results in this case in the relation γc = 2(c- 1) for the Grüneisen parameter in this region. Experimental data for the zero pressure value Γo and its derivative Γo together with theoretical data for the limiting value γ∞ = 2/3, and the additional expenmental value γc are then used to determine the thermal (phonon) pressure with the common Mie-Grüneisen assumption. 相似文献
5.
The general expression for the Anderson-Grüneisen parameterδ recently derived by Gupta and others, has been used to study the variation ofδ with the Grüneisen parameterγ employing the interaction approach. For this purpose four potential energy functions have been selected. It is found thatδ values evaluated by the modified Varshni-Shukla potential are better than other forms of overlap repulsive interaction. The
variation ofδ withγ is also studied by plotting curves betweenδ andγ. The method of least-squares has been employed to yield the best fitted equation. 相似文献
6.
The lattice parameters of CdF2 andβ-PbF2 have been determined over the temperature range 300–670 K. The coefficient of expansion at room temperature is 21·3 × 10−6 K−1 and 25·4 × 10−6 K−1 for CdF2 and PbF2 respectively and it increases linearly with temperature over the range of temperature covered. The Grüneisen parameter decreases
with temperature in both the crystals. 相似文献
7.
A revised model of volume dependence of Anderson–Grüneisen parameter for lower mantle under adiabatic condition is presented in this study, and the volume dependence of (α T/C P =α ′) is then discussed. It is shown that the results are in good agreement with seismic data of the Earth. 相似文献
8.
We present a new method for understanding the changes with temperature of the volume and compressibility of solids. These changes depend on five parameters: V 0, B 0, Θ, γ G and δ T. V 0 and B 0 are the atomic volume and bulk modulus at T?=?0?K, Θ is the Debye temperature, γ G is the Grüneisen parameter, and δ T is the Anderson–Grüneisen parameter. Equations for the temperature-dependent volume, bulk modulus and thermal expansion are given, and examples of the use of these equations are provided, with particular emphasis on the light actinides. For the elements, we examine the relationship between experimental values of γ G and δ T, and find no clear correlation. In particular, Swenson's rule, which states that the bulk modulus does not change with temperature if the volume is held constant, is a poor approximation to the data. We reveal a new useful approximate relationship between dB/dP and γ G. We find that the thermodynamic quantity q, which describes the variation in γ G with volume, distributes around 2, not around 1, as often assumed. We show that the thermal- expansion behavior of Si and Ge (including negative thermal expansion at low temperatures) are well described with the use of a two-level invar model. 相似文献
9.
10.
The Thomas–Fermi approximation gives the Grüneisen parameter γ=γ∞=1/2 for all materials at extreme compression (P→∞ or V→0). After re-analyzing the existing experimental data of volume dependence of Grüneisen parameter γ of hexagonal close-packed (HCP) iron, we find that γ=1/2+a(V/V 0)1/3+b(V/V 0) n , where a, b and n are constants. Based on this new form of γ, the second Grüneisen parameter q, the Debye temperature θD and the shear sound velocity v s of HCP iron are discussed in the present work. It is found that the zero pressure second Grüneisen parameter q 0=0.654, which is consistent with the previously determined value of HCP iron for Earth's core physics from Dubrovinsky et al. The calculations for the Debye temperature and the shear sound velocity are also found to be in good agreement with the experimental data. 相似文献
11.
Semiempirical equations of state (EoS) of Au, Pt, MgO, NaCl-B1, and NaCl-B2 based on expanded Mie–Grüneisen–Debye approach, which are consistent both with the Mie–Grüneisen–Bose–Einstein approach and the thermochemical, X-ray, ultrasonic and shock-wave data in a wide pressure-temperature range, have been constructed. It is shown that to determine the volume dependence of the Grüneisen parameter, not only shock-wave and static compression data, but also experimental information on heat capacity, bulk moduli, volume, and thermal expansion coefficient at zero pressure need to be taken into account. Intrinsic anharmonicity is of great importance at construction of EoS at high temperatures and x=V/V 0>1. Cross-comparison of the current equations of state with independent measurements shows that these EoS may be used as the internally consistent and independent pressure scales in a wide range of temperatures and pressures. 相似文献
12.
13.
B K Sharma 《Pramana》1991,37(6):489-496
The isochoric temperature derivative of sound velocity, Beyer’s nonlinearity parameter, the isothermal volume derivatives
of thermodynamic Grüneisen parameter and isochoric heat capacity and the repulsive exponent of intermolecular potential are
shown to be related to the molecular constant representing the ratio of internal pressure to cohesive pressure of liquids.
The calculated values are reasonably satisfactory and explain the experimental results on sound propagation data of liquids.
The results have been used to develop further understanding of the significance of molecular constant, fractional free volume
and repulsive exponent of intermolecular potential in describing various thermoacoustic and nonlinear properties and the anharmonic
behaviour with regard to molecular order and intermolecular interactions in liquids. 相似文献
14.
B K Sharma 《Pramana》1980,14(6):477-483
We test the validity of an approximate equation of state of real fluids and the expression for surface tension of hardsphere
liquids with attractive interactions derived by Sharma and others by obtaining expressions for isothermal compressibility,C
1-parameter and acoustical parameter and relate them to microscopic Grüneisen parameter. The calculated values for liquid fluorine
show fair agreement with experimental values. 相似文献
15.
The pressure dependence of thelo-to phonons in InAs has been investigated by Raman scattering using the diamond anvil cell. Indium arsenide transforms, presumably
to the rock-salt structure at 70±1 kbar. The mode Grüneisen parameters for thelo-to phonons are γ
lo
=0.99±0.03, γ
to
=1.2±0.03 respectively. The effective charge,e*
T
, for InAs decreases slightly with pressure and this trend is in accordance with the behaviour of other III–V zinc blende
structured semiconductors: The structural phase transition is discussed in the light of theoretical calculations for phase
stability of III–V compounds, as well as recent high pressure x-ray diffraction studies. 相似文献
16.
17.
采用化爆加载,以黄铜为飞片、无氧铜为靶板,测量了以抗氢钢(HR2)、重玻璃(SiO2)、铝合金(LY12/LF6)、镁铝合金(MB2)、有机玻璃(PMMA)和空气(Air)为垫块(Anvil)材料中的冲击波速度(上述材料的Hugoniot状态参数C0、λ均为已知),由此确定了无氧铜的等熵卸载路径。结果表明:在冲击态(即初始卸载态)高达219 GPa的压力范围内,无氧铜的等熵卸载过程可用Grüneisen状态方程在ργ=ρ0γ0近似下作很好的描述;各条卸载路径到一个大气压的终态粒子速度US与镜像反演的粒子速度2u的偏差(US-2u)/(2u),随冲击波压力的增加而增大。 相似文献
18.
《Physics letters. A》2020,384(1):126035
Lightweight carbon materials with excellent thermal and mechanical properties have important applications in aerospace industry. In this study, the stability, mechanical properties, lattice thermal conductivity, electronic structure, infrared and Raman spectrum of sp3 hybridized low-density fullerite C24 were investigated according to density functional theory (DFT) calculations. It was found that the fullerite C24 was both thermodynamic and dynamic stable. Quasi-harmonic approximation and Grüneisen parameter calculations clarified why the fullerite C24 had a positive thermal expansion coefficient at low temperature. The fullerite C24 also exhibited excellent mechanical properties. Interestingly, the Vickers hardness of carbon allotropes was found to almost be linear proportional to the density of a carbon material. HSE06 electronic structure calculations showed that it was a semiconductor with direct bandgap of 2.56 eV. Anharmonic lattice dynamic calculations showed that its thermal conductivity was higher than semiconductor silicon. Besides, Raman and infrared active modes as well as the corresponding spectra were presented. 相似文献
19.
20.
B K Godwal 《Pramana》1982,19(3):225-229
The method of first principle pseudopotential is used to simulate the volume variation of nuclear Grüneisen parameter. The
elements Al and Be, for which Neal’s experimental data exist are investigated. The nuclear Grüneisen obtained from the details
of phonon frequencies are in better agreement with the experimental data as compared to those obtained from approximate Slater
and Dugdale-MacDonald methods, often used in shock wave studies. 相似文献