Wolf-Dietrich Kraeft

A quantum kinetic equation for nonideal gases in the three-particle collision approximation

A quantum mechanical version of a kinetic equation is derived which accounts for three-particle collisions. It is shown that the total energy is conserved in the binary collision approximation.

Ionization-potential depression and dynamical structure factor in dense plasmas

The properties of a bound electron system immersed in a plasma environment are strongly modified by the surrounding plasma. The modification of an essential quantity, the ionization energy, is described by the electronic and ionic self-energies, including dynamical screening within the framework of the quantum statistical theory. Introducing the ionic dynamical structure factor as the indicator for the ionic microfield, we demonstrate that ionic correlations and fluctuations play a critical role in determining the ionization potential depression. This is, in particular, true for mixtures of different ions with large mass and charge asymmetry. The ionization potential depression is calculated for dense aluminum plasmas as well as for a CH plasma and compared to the experimental data and more phenomenological approaches used so far.

Bound States in Coulomb Systems - Old Problems and New Solutions

We analyze the quantum statistical treatment of bound states in Hydrogen considered as a system of electrons and protons. Within this physical picture we calculate analytically isotherms of pressure for Hydrogen in a broad density region and compare to some results from the chemical picture. Our study is restricted to the range of intermediate temperatures 104K < T < 105K and not too high densities n < 1024 protons per cm3, the formation of molecules is neglected. First we resume in detail the two transitions along isotherms: (i) formation of bound states occurring by increasing the density from low to moderate values, (ii) the destruction of bound states in the high density region, modelled here by Pauli-Fock effects. Avoiding chemical models we will show, why bound states according to a discrete part of the spectra occur only in a valley in the T-p plane. First we study virial expansions in the canonical ensemble and then in the grand canonical ensemble. We show that in fugacity representations the population of bound states saturates at higher density and that a combination of both representations provides quickly converging equations of state. In the case of degenerate systems we calculated first the density-dependent energy levels, and find the pressure in Hartree-Fock-Wigner approximation showing the prominent role of Pauli blocking and Fock effects in the selfenergy (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Equation of state and correlation energy of dense plasmas

In this paper, the method of thermodynamic Greens functions is applied to investigate thermodynamic properties of dense weakly coupled plasmas. First, we present results for the equation of state for fully ionized hydrogen and compare our results with path integral Monte Carlo simulation data. Densities and temperatures are considered where correlations as well as Fermi statistics have to be taken into account. Then, the correlation energy and the mean value of the kinetic energy of dense plasmas are considered. Usually one finds that the kinetic energy is larger than that of an ideal system due to the interaction. However, in agreement with results from quantum simulations, we found, for certain densities and temperatures, a lowering of the kinetic energy.

Quantum Statistics of Many-Particle Systems

The properties and the behaviour of systems composed of many elementary particles, atomic nuclei, atoms etc. are described by the quantum statistics. We assume that the reader is familiar with the most important features of quantum theory and statistical mechanics (see, e.g., Dirac, 1958; Messiah, 1961; Fick, 1968; Landau and Lifshits, 1967). Therefore in this chapter we will give only a brief introduction to this field, in order to explain the main ideas, relations and notations.

Ionization potential depression and optical spectra in a Debye plasma model

We show how optical spectra in dense plasmas are determined by the shift of energy levels as well as by the broadening due to collisions with the plasma particles. In the lowest approximation, the interaction with the plasma particles is described by the random phase approximation (RPA) dielectric function, leading to the Debye shift of the continuum edge. The bound states remain nearly un-shifted, and their broadening is calculated in the Born approximation. The roles of ionization potential depression as well as the Inglis–Teller effect are shown. The model calculations have to be improved going beyond the lowest (RPA) approximation when applying to warm dense matter spectra.

Reply to "Comment on 'Direct linear term in the equation of state of plasmas' ".

The long-standing discrepancy in the equation of state of charge neutral plasmas, the occurrence of an e(2) direct term in the second virial coefficient, is dealt with. We state that such a contribution should not appear for a pure Coulomb interaction.

Equation of state of high density plasmas

We present results on the equation of state (EOS) of high density hydrogen plasmas. We use a hybrid first principles method capable of describing fully ionized plasmas. Electrons as well as the electron–ion interactions are described with Greens functions technique which includes dynamic screening and degeneracy effects. The properties of the proton subsystem are calculated using classical integral equations (HNC) which take strong correlations into account. We compare our results to a variety of analytic approaches and simulation techniques.

Quantum statistical approach to dense, weakly coupled plasmas

We present a quantum equation of state (EOS) which is applicable to weakly coupled systems of any density and temperature. As an example, we consider the EOS of hydrogen. We include strong ion‐ion correlations through HNC‐calculations. We study the influence of correlation effects on the mean kinetic energy.

THERMODYNAMICS AND TRANSPORT IN DENSE PARTIALLY IONIZED PLASMAS

It is shown on the basis of Green functions technique that macroscopic properties of partially ionized plasmas are essentially determined by the Coulomb interaction and by the symmetry postulate. Especially the many particle effects such as screening, self energy and modifications of the two particle spectrum lead to drastic changes of the plasma features as compared with those in dilute systems.