H. Juranek

Self-consistent fluid variational theory for pressure dissociation in dense hydrogen

Recent developments in shock-wave experimental techniques have allowed the 100 GPa pressure range in hydrogen to be probed. In recently reported single-shock-wave laser-driven experiments, the principal Hugoniot was determined up to 300 GPa. It has been shown that dissociation of hydrogen molecules becomes operative under such ultrahigh pressures. Various models have been developed which treat pressure dissociation approximately. In this paper we generalize standard fluid variational theory to a two-component system with a reaction (dissociation). From the free energy, other thermodynamic functions such as the internal energy and entropy are derived. Comparison with other approaches and the shock-wave data is performed.

Fluid variational theory for pressure dissociation in dense hydrogen: Multicomponent reference system and nonadditivity effects

In a recent paper, standard hard-sphere variational theory has been applied to pressure dissociation in dense fluid hydrogen (Juranek and Redmer, J. Chem. Phys. 112, 3780 (2000)). The correlation contributions to the dissociation equilibrium were determined from the free energy functional using effective pair potentials and minimization with respect to the hard-sphere reference system. For simplicity, the Berthelot mixing rule was used to determine the H–H2 pair potential (which entails additive effective hard spheres), and single-component reference pair correlation functions were employed for evaluating the correlation integrals. In this paper, we employ multicomponent reference pair correlations, and we study the sensitivity of the results with respect to nonadditivity of the effective hard spheres. We compare our results with available ab initio simulation data.

Equation of state for dense hydrogen and helium: application to astrophysics

We present theoretical results for the equation of state of hydrogen and helium applying the chemical picture which treats the elementary charged particles (electrons, ions) and neutral bound states (atoms, molecules) on an equal footing. The chemical equilibrium for dissociation and ionization processes is solved accounting for nonideality corrections. We compare our results with experiments and other theoretical models and calculate pressures and temperatures in jupiters interior.

Equation of State for Dense Hydrogen

We use equations of state for hydrogen in the dense fluid and the fully ionized plasma state to evaluate the intermediate region where partial dissociation and ionization occurs. We calculate the Hugoniot curve within both models and compare with experiments and other theories. The sound velocity is determined in the warm fluid domain. Based on this approach, the composition of dense hydrogen can be calculated for given densities and temperatures.

Metallization of hydrogen using heavy ion imploded multi-layered cylindrical targets

This paper shows with the help of two-dimensional hydrodynamic simulations that it may be possible to achieve theoretically predicted physical conditions required for hydrogen metallization in heavy ion imploded multi-layered cylindrical targets. These include a density of about 1 g/cm 3 , a pressure of 2-5 Mbar and a temperature of a few 0.1eV in the compressed hydrogen sample. In this study an intense uranium beam consisting of 10 12 ions having a particle energy of 400 MeV/u is considered. The ions are delivered in a single bunch that has a length of 50 ns. These beam parameters are the design parameters for the future 200 Tm synchrotron facility, SIS-200, that will be constructed at the Gesellschaft fur Schwerionenforschung (GSI), Darmstadt.

The creation of strongly coupled plasmas using an intense heavy ion beam: low-entropy compression of hydrogen and the problem of hydrogen metallization

Intense heavy ion beams deposit energy very efficiently over extended volumes of solid density targets, thereby creating large samples of strongly coupled plasmas. Intense beams of energetic heavy ions are therefore an ideal tool to research this interesting field. It is also possible to design experiments using special beam–target geometries to achieve low-entropy compression of samples of matter. This type of experiments is of particular interest for studying the problem of hydrogen metallization. In this paper we present a design study of such a proposed experiment that will be carried out at the future heavy ion synchrotron facility SIS100, at the Gesellschaft fur Schwerionenforschung, Darmstadt. This study has been done using a two-dimensional hydrodynamic computer code. The target consists of a solid hydrogen cylinder that is enclosed in a thick shell of lead whose one face is irradiated with an ion beam which has an annular (ring shaped) focal spot. The beam intensity and other parameters are considered to be the same as expected at the future SIS100 facility. The simulations show that due to multiple shock reflection between the cylinder axis and the lead–hydrogen boundary, one can achieve up to 20 times solid density in hydrogen while keeping the temperature as low as a few thousand K. The corresponding pressure is of the order of 10 Mbar. These values of the physical parameters lie within the range of theoretically predicted values for hydrogen metallization. We have also carried out a parameter study of this problem by varying the target and beam parameters over a wide range. It has been found that the results are very insensitive to such changes in the input parameters.

Equation of state for hydrogen and helium in the chemical picture

Shock experiments have reached the megabar pressure range and temperatures typical in planets such as Jupiter. The equation of state and other material properties such as electrical conductivity are needed for hydrogen and helium in order to model such objects. We develop an equation of state that considers pressure dissociation and ionization. We make use of fluid variational theory and Pade approximations. A chemical picture is applied considering the species electrons, protons, atoms and molecules. Comparison with experimental equation of state data is presented.

Equation of State and Electrical Conductivity of Dense Fluid Hydrogen and Helium

Abstract The equation of state of fluid hydrogen, helium, and their mixtures is determined within fluid variational theory. Reactions between the constituents such as dissociation and ionization are considered. Results are given for densities and temperatures relevant for the interior of giant planets. Furthermore, the electrical conductivity is determined within linear response theory. Comparison is performed with available experiments and other theoretical work.

Warm Dense Hydrogen in the Chemical Picture

We present theoretical results for the equation of state and the reflectivity of hydrogen in the high pressure domain. Based on the chemical picture, the equation of state is determined within fluid variational theory considering dissociation and ionization processes as well. We compare our results with shock‐wave data and other theoretical predictions for the Hugoniot curve and the speed of sound. We have calculated the electrical conductivity along the Hugoniot curve and determined the reflectivity within the Drude model. The nonmetal‐to‐metal transition found is in agreement with experimental data.