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91.
Lin Zhang Ying-Hua LiYu-Ying Yu Xue-Mei LiYun Ma Cheng-Gang GuCheng-Da Dai Ling-Cang Cai 《Physica B: Condensed Matter》2011,406(22):4163-4169
The mean-field potential (MFP) approach is an efficient way to evaluate the free energy contribution of ion motions for both solid and liquid states. In this paper the MFP is generally constructed with a volume-dependent term and a shape function. The former is derived in accordance with quasi-harmonic approximation. The latter is given semi-empirically. Application to multiphase equations of state for β-, γ- and liquid-tin has been examined. The theoretical phase diagram and thermodynamic properties of isotherm, thermal expansion, heat capacity, Hugoniot states as well as phase transitions are all in excellent agreement with experiments. 相似文献
92.
93.
用金刚石压砧高压X光衍射技术研究了Ⅱ-Ⅵ族化合物CdTe的室温状态方程和室温高压相变。实验的最高压力达39.2 GPa。实验中发现CdTe从(3.3±0.1)GPa开始从闪锌矿结构相相NaCl结构相转变,相变时体积收缩15.8%;从(10.3±0.2)GPa开始从NaCl相向β-Sn结构相转变,相变时无体积突变;在(12.2±0.2)GPa由β-Sn相向正交结构相转变,相变时也无体积突变。CdTe的压缩数据用最小二乘法以Bridgman状态方程和Murnaghan状态方程拟合,得到其零压时合相变压力时各个相的体弹模量及体弹模量的压力微商,并与其它的实验合理论结果进行比较。 相似文献
94.
95.
D.V. Fisher Y. Maron 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,14(3):349-359
Accurate treatment of the plasma density effects requires a detailed knowledge of the spatial distribution of individual ions
around a test ion. In the present work, rigorous expressions are derived for the main 2- and 3-particle spatial distribution
functions involving the nearest neighbor (NN) and the next-nearest neighbor (NNN) ions. These expressions, valid for both
ideal and nonideal plasmas, present the distributions as functionals of the potentials U
NN and U
NNN at the nearest and next-nearest ion locations. All of the distribution functions except one are derived and discussed in
the present work for the first time ever. For utilization of our results in practical calculations, we suggest semi-empirical
expressions for U
NN and U
NNN in the ion-ion coupling parameter range 0 ?Γ < 1. In order to test the accuracy of our expressions for U
NN and U
NNN we conduct Molecular Dynamics (MD) simulations. The simulations utilize the pure Coulomb particle-particle interaction potentials,
regularized at close range to avoid classical Coulomb collapse, and are free from the assumptions made to find U
NN and U
NNN. Thus, the results of the MD simulations provide an independent test of our theoretical results. Excellent agreement has
been found between the results of the theory and of the MD simulations. Finally, we outline the implications of the present
findings on the problem of tunneling and charge exchange in dense plasmas.
Received 27 October 2000 and Received in final form 30 January 2001 相似文献
96.
R. Ramakumar K. Yamaji 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(1):71-75
A simple model is developed to understand superconductivity in α
′
-TTF[Pd(dmit)2]2. We include electron-intra molecular and intermolecular phonon interactions as the mechanism of superconductivity. Intramolecular vibrations included are the eight symmetric Ag modes of the Pd(dmit)2 molecule. Intermolecular vibrations included are the longitudinal acoustic and transverse acoustic (LA and TA) modes of the Pd(dmit)2 column. All the electron-phonon coupling constants are calculated from first principles. We find that largest el-intramolecular vibration coupling is to the Ag mode with the highest frequency (1449 cm-1). The el-intermolecular coupling to the LA mode is found to be larger than the total el-intramolecular couplings. We also find el-(TA)phonon coupling to be at least an order of magnitude smaller than el-(LA)phonon coupling.
Estimate of superconducting transition temperature is comparable to experimental result. We also provide a detailed discussion,
employing the results of recent numerical calculations on two-chain Hubbard model and the specific material parameters, on
the relative importance of el-ph and Coulomb-origin mechanisms of superconductivity in α
′
-TTF[Pd(dmit)2]2 and TTF[Ni(dmit)
2
]
2
.
Received 29 March 2001 and Received in final form 7 August 2001 相似文献
97.
FAN Hong-Yi WANG Hui 《理论物理通讯》2001,(10)
We discuss the entanglement swapping of two pairs of displaced two-mode squeezed states and find that the squeezing parameter of the outcoming squeezed state is less than that of the originM squeezed states. The calculation is greatly simplified by virtue of the natural expression of the two-mode squeezing operator in EPR eigenstate representation. A protocol for such entanglement swapping is proposed.`` 相似文献
98.
The different approximations that have been used in applying Bethe’s cluster model to the nematic-isotropic phase transition
are examined. It is shown that the introduction of a higher order term in the mean field potential of an outer molecule of
the cluster improves the consistency of the theory considerably. In particular, the importance of satisfying Chang’s relation
is emphasized. Calculations are presented of the long and short range order parameters, heat of transition and specific heat
for different values ofz, the number of nearest neighbours around any given molecule, for both nonpolar and antiparallel near neighbour correlations.
Even the new mean field potential appears to be inadequate forz=3. 相似文献
99.
本文根据量子力学的线性叠加原理,构造了由多模(即q模时目平态的相反态|{{-Zj}〉q及多模虚相干态|{{-Zj}〉q这两者的线性叠加所组成的一种新型的多模Schrodinger猫态光场利用新近建立的多模压缩态理论,研究了态的N次方Y压缩效应,结果发现:①当压缩阶数N=Zp且p=2m(m=1,2,3,…,…)时,态。总是恒处于N-Y最小测不准态;②当压缩阶数N=2p且p=2m+1(m=0,1,2,3,…,…)时,如果各模的初始相位,态间的初始相位差以及各单模相干态光场的平均光子数之总和等满足一定的量子化条件,则态可呈现出周期性变化的、任意阶的N次方Y压缩效应;③当压缩阶数N=2P'+1时,无论p'=2m(m=0,1,2,…,…)还是p'=2m+1(m=0,1,2,3,…,……),只要各模的初始相位满足一定的量子条件,则当两态叠加几率幅满足时,态就恒处于N-Y测不准态,始终不呈现N-Y最小测不准态和N次方Y压缩;而当时,态始终不呈现N-Y测不准态、N-Y最小测不准态和N次方Y压缩效应. 相似文献
100.
Influence of Hydrothermal Temperature on Structures and Photovoltaic Properties of SnO2 Nanoparticles 总被引:1,自引:0,他引:1
Liu Yang Yang Jihua Yang Wensheng Xie Tengfeng Bai Yubai Li Tiejin 《Journal of nanoparticle research》2000,2(3):309-313
Two SnO2 nanoparticles were synthesized by hydrothermal method at 170°C and 180°C, respectively. Transmission electron microscope observations reveal that the diameters of both the nanoparticles are around 6nm. At the same time, surface photovoltage spectroscopy measurements show that the nanoparticle synthesized at 180°C has more surface electronic states at 0.3eV below the conduction band than the one synthesized at 170°C. This means that the temperatures chosen in hydrothermal synthesis have significant influence on the surface electronic characteristics of resultant SnO2 nanoparticles but the effect on their sizes is not obvious. However, after being calcined at 500°C for 2h, the diameter of the nanoparticle synthesized at 180°C increased to 23nm and that of the nanoparticle synthesized at 170°C increased to 32nm as calculated from X-ray diffraction pattern. 相似文献