Equation of state of hydrogen,helium, and solar plasmas

The equation of state (EOS) for plasmas of the two lightest elements H and He, and mixtures as typical for the plasmas in the sun are calculated. The contributions of deep bound states are included by using inverted fugacity expansions. The inversion of fugacities to densities is reduced to solvable algebraic problems and expressed by rational polynomials. The calculation of relative pressures is carried out separately for low and high densities. Near the crossing point, in between, the separate solutions are connected to each other by smooth concatenation. Applications to hydrogen–helium plasmas in the sun including estimates for the isentropic EOS are discussed.     

Equation of state of fluid helium at high temperatures and densities

Hugoniot curves and shock temperatures of gas helium with initial temperature 293 K and three initial pressures 0.6, 1.2, and 5.0 MPa were measured up to 15000 K using a two-stage light-gas gun and transient radiation pyrometer. It was found that the calculated Hugoniot EOS of gas helium at the same initial pressure using Saha equation with Debye-Hückel correction was in good agreement with the experimental data. The curve of the calculated shock wave velocity with the particle velocity of gas helium which is shocked from the initial pressure 5 MPa and temperature 293 K, i.e., theD ≈u relation,D=C ₀+λu (u<10 km/s, λ=1.32) in a low pressure region, is approximately parallel with the fittedD ≈u (λ=1.36) of liquid helium from the experimental data of Nellis et al. Our calculations show that the Hugoniot parameter λ is independent of the initial density p{in0}. TheD≈u curves of gas helium will transfer to another one and approach a limiting value of compression when their temperature elevates to about 18000 K and the ionization degree of the shocked gas helium reaches 10⁻³.     

Equation of state of fluid helium at high temperatures and densities

Helium, hydrogen, and their isotopes are the simplest monoatomic and diatomic molecules. It is relatively easy to describe their properties using the basic principles of quantum mechanics. In condensed matter physics, hydrogen and helium serve as the models for the condensed matter properties at extreme conditions so that both experi- mental and theoretical physicists pay much attention to the study of their properties[1], especially the insulator-metal transition of hydrogen[2]. The aim to st…     

Equation of state and interaction potential of helium under high temperatures and high densities

Based on the thermodynamics statistic method, the improved variational perturbation theory and the modified quantum mechanics correction model have been used to calculate the equation of state of liquid helium at pressure from 0.7 to 108 GPa. The calculation results are in good agreement with the experimental data. The EXP-6 potential (α = 13.1) can more accurately describe the interaction of helium atoms than other potentials in the scheme. Finally, a comparison is shown between our interatomic potentials and other potentials.     

Electrical conductivity and thermopower of metallic helium

The pair effective interionic interaction, electrical resistance, and thermopower of liquid metallic helium have been calculated over wide temperature and density ranges using the perturbation theory for the potential of electron-ion interaction. For conduction electrons, the random-phase approximation has been used taking into account the exchange interaction and correlations in the local-field approximation. The nuclear subsystem has been described by the hard-sphere model. The sphere diameter is the only parameter of the theory. The diameter and the system density at which helium is transformed from the singly ionized to doubly ionized state have been estimated based on an analysis of the pair effective interaction between helium nuclei. The case of doubly ionized helium atoms has been considered. The numerical calculations have been performed taking into account the perturbation theory in terms up to the third order. In all cases, the role of the third-order correction is significant. In the case of metallic helium, the values of the electrical resistance and its temperature dependence are characteristic of divalent simple liquid metals, as well as the dependences of the thermopower on the density and temperature.     

The metallic state

Metals contain free electrons. Various theoretical and practical implications of this characteristic feature of the metallic state are discussed. Recent views which emphasize ease of ionization, unsaturated metallic bonds, and screening of electrical charges by free electrons, as the basis for distinguishing between metals, semi-conductors, and insulators, are described. The importance of the free electron bond for the crystal structures, cohesive properties, and alloy behaviour of metals is emphasized, and the principles underlying the engineering strength properties of matter and the design of creep-resistant alloys are briefly discussed in terms of free electrons and dislocations in solids.     

Swelling of metallic surfaces irradiated by helium ions

At doses close to threshold for exfoliation or bubble formation the surfaces have been investigated by SEM and, after isolation of surface layers, also by RBS. Swelling as a function of energy and material has been determined. The data are interpreted in the form of volume occupied by a helium atom. We find an indication for a volume decrease with increasing energy. A special example of blister formation is also discussed, where we find evidence for a non-uniform fracture plane.     

氦原子基态能量的Roothaan-Hartree-Fock计算

采用包含两个斯莱特基的"双ζ"函数说明了利用自洽场法求解基态氦原子Roothaan-Hartree-Fock方程的数值过程,计算得基态能量为-2.862 568 Hartree.利用基态的对称性,提出了通过求解泊松方程来计算库仑算符的方法,给出了交叠矩阵和单电子算符的矩阵元,并对自洽的标准作了讨论.     

The Fulde-Ferrell state in superfluid helium

The Fulde-Ferrell state in a superfluid³He-⁴HeII solution is investigated. Starting from its broken symmetry, a relative translation-gauge symmetry, the linearized hydrodynamic equations to lowest order in wave number are presented. To this order, the superfluid current perpendicular to the preferred direction vanishes identically; at the same time, supercurrents generated by a uniform change in temperature or density become possible. The Goldstone mode of the Fulde-Ferrell state is shown to be a propagating spin-temperature-shear wave.     

Structure of metallic nanowires and nanoclusters formed in superfluid helium

It is shown that metallic nanowires (5–8 nm in diameter) that form during laser ablation of Ni, Pb, In, and Sn targets embedded in HeII contain extended single-crystal segments, while spherical clusters (about 2 μm in diameter) that form under these conditions have a regular shape and an atomically smooth surface. Such structures are explained by melting of metal ablation products under their coalescence in HeII. The short-term action of a low-intensity beam of electrons with an energy of 200 keV initiates the explosion in metallic spheres preserved in the vacuum chamber of a transmission electron microscope, which is accompanied with the formation of thousands of clusters with a diameter of a few nanometers. This effect is due to metastability of internal mechanical stresses produced upon sharp cooling of molten spheres by liquid helium. A mechanism of condensation of atoms and nanoparticles in quantized vortices of superfluid helium is proposed.     

Properties of the finite-mass helium ground state

ABSTRACT

We describe a simple method of incorporating the finite mass of the nucleus directly into atomic variational Monte Carlo calculations. To test this algorithm we computed the energy and 20 other properties of ⁴He. We then compared these values with those obtained from our earlier infinite nuclear mass algorithm. All of our expectation values are in excellent agreement with previous results on this system.     

氦原子高激发态的塞曼效应

利用塞曼哈密顿的球张量形式以及塞曼哈密顿在耦合表象中的矩阵元公式,在考虑磁场二次项作用的基础上,研究了氦原子n3P(n=4,5)高激发态的塞曼效应,给出解析解,并绘出了塞曼能级分裂图.     

Pseudopotential approach to the embedding of helium atoms in metallic jellium

Using the Coupled Hartree-Fock (CHF) method, we calculate the energy change, E, in embedding a helium atom into a metallic jellium. This energy change is expressed as a series in the free electron density, ϱ₀, of the metal under the assumption that, upon embedding, no changes take place within the helium atom. Keeping the leading term of this series, the well-known result E = αϱ₀ is obtained. The constant α is expressed in terms of the characteristics of the 1s orbital of the free helium atom; this is found to be 590 eV a₀³ which however is greater than the value of 385 eV a₀³ predicted by the exact Hartree-Fock solution.     

Properties of surface state electrons on liquid helium

Electrons on the surface of liquid helium form a two-dimensional system that is of great interest for its own unique properties as well as being a probe of the helium surface. The spectroscopic evidence for the hydrogenic nature of the surface state is compared with predictions. Measurements of the electron mobility parallel to the surface in low and high electric fields are compared with theory. The lifetime in the surface state is discussed as well as the effect of the electron on the liquid surface. The possibility that the electrons crystallize to form a two-dimensional lattice and the properties of this lattice are also analyzed.     

Superconducting state parameters of binary metallic glasses

Ashcroft’s empty core (EMC) model potential is used to study the superconducting state parameters (SSPs) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature T _C , isotope effect exponent αand effective interaction strength N _O V of some binary metallic glasses based on the superconducting (S), conditional superconducting (S’) and non-superconducting (NS) elements of the periodic table. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid et al. (F) and Sarkar et al. (S) are used for the first time with EMC potential in the present investigation to study the screening influence on the aforesaid properties. The T _C obtained from the H-local field correction function are in excellent agreement with available theoretical or experimental data. In the present computation, the use of the pseudo-alloy-atom model (PAA) was proposed and found successful. Present work results are in qualitative agreement with such earlier reported experimental values which confirm the superconducting phase in all metallic glasses. A strong dependency of the SSPs of the metallic glasses on the valence ‘Z’ is identified.      

Equation of state of hollandite type-structure

Abstract

The room-temperature compression of BaFeMn₇O₁₆hollandite has been determined to 519 kbar with X-Ray methods. With a 1-bar molar volume of V₀=339±2 cm³/mol and a Birch-Murnaghan equation of state, we obtain for the bulk modulus K'₀=2304±150 kbar and for the pressure derivative K'₀=1.73±0.45.If these moduli are typical of a hollandite structure, then the high-pressure density of the Ca_0.5Mg_0.5Al₂Si₂O₈pseudo-hollandite could be similar to those of silicates with a perovskite structure.     

Equation of state of real gases

The pressure for systems with small z, whose interaction is stable and rapidly decreasing, is written as a functional of the correlation functions. The differential equation of state is obtained for such systems. The integration of this equation leads to the generalized virial expansion.     

Equation of state of condensed media

A new choice is proposed for the generating functional which is used to obtain an integral equation for the radial distribution function that is valid in the domain of dense fluids. The corresponding equation of state for giving the intramolecular potential in the form (r)r ^–s agrees in the case of dense fluids with the known Tait empirical equation of state. The Tait equation is extended to the high-pressure case. Processing the experimental data for water exhibits good agreement between the equation of state obtained and experiment in the pressure range from 10⁵–10⁹ Pa.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 43–47, December, 1981.     

Equation of state of superdense matter

The possibility of the existence of anomalous nuclei in superdense stars as well as the possibility of the spontaneous transition of a superdense object as a whole into an anomalous state which can be due either to the Migdal or the Lee mechanisms are discussed. An equation of state is obtained for _Nucl by using data on the total proton-proton scattering cross section in the high-energy range.Translated from Izvestiya Vysshikh Uchbenykh Zavedenii, Fizika, No. 11, pp. 20–23, November, 1978.