Principal Hugoniot Curve Research Articles

Optical properties of water at high temperature

We calculate optical properties of water along the principal Hugoniot curve from ambient conditions up to temperatures of 130 000 K with density functional theory (DFT) and the Kubo-Greenwood formula. The effect of the exchange correlation functional is examined by comparing the generalized gradient approximation with a hybrid functional that contains Fock exchange. We find noticeable but moderate differences between the respective results which decrease rapidly above 80 000 K. The reflectivity along the principal Hugoniot is calculated and a good qualitative but fair quantitative agreement with available experimental data is found. Our results are of general relevance for calculations of optical properties with DFT at zero and elevated temperature.

Estimating the quantum effects from molecular vibrations of water under high pressuresand temperatures

We present a simple model which estimates the influence of quantum effects from molecularvibrations on the equation of state of water under high pressures and temperatures. Thismodel is combined with an ab initio equation of state of water generated by quantummolecular dynamics (QMD) simulations employing density functional theory for theelectrons and a classical algorithm for the ions. We calculate the specific heat capacity aswell as the principal Hugoniot curve, especially the Hugoniot temperature, in accordancewith experiments.

Electrical Conductivity of Noble Gases at High Pressures

AbstractWe present experimental and theoretical results for the electrical conductivity of noble gases (He, Ne, Ar, Kr, Xe) up to high pressures where a transition from nonmetallic to metallic‐like conductivities occurs. In addition, we show the behavior of the thermal conductivity and thermopower for xenon as an example. The experiments were performed using explosively driven shock waves. Different geometries allow to probe various parameter regions up to several megabars. Besides single‐shock experiments along the principal Hugoniot curve, also multiple‐shock experiments were performed which follow almost an isentrope. The theoretical calculations were performed within a partially ionized plasma model. The composition is determined by solving a system of mass action laws. The transport coefficients are calculated within linear response theory taking into account the relevant scattering mechanisms of electrons at different ion species, atoms, and other electrons. The general trends of the experimental results can be explained within this theoretical approach. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Generation of a double shock driven by laser

The feasibility and reliability of a multiple laser shock generation to study the equation of state surface off the principal Hugoniot curve and to approach an isentropic compression has been demonstrated. The technique is based on the use of a double laser pulse. A strong shock was generated in iron targets precompressed by a first weak shock. The effect of precompression was studied. The experiment was performed at the Laboratoire pour l'Utilisation des Lasers Intenses laboratory.

Reconstruction of Ross' linear-mixing model for the equation of state of deuterium

The linear mixing (LM) model proposed by Ross [Phys. Rev. B 58 (1998) 669] can accurately reproduce experimental Hugoniot data for shocked liquid deuterium at pressures up to 6 Mbar. Using a simple dissociation scheme, the model smoothly interpolates between (or linearly “mixes”) a molecular fluid equation of state (EOS) applicable at low pressures, and a metallic-like description valid under more extreme conditions, with the relative composition of the mixture determined by minimizing the total Helmholtz free energy of the system. Although the formulation of the LM model is straightforward, it nevertheless involves a series of nontrivial computations and results whose details are fragmented in the published literature. We present an explicit and self-contained reconstruction of the LM model, and correct minor typographical errors that appeared in the original publications. Limitations of Ross' approach and comparisons with popular alternate theories are also discussed, although no attempt is made to conduct a thorough survey of existing EOS models for deuterium. Listings of the Mathematica codes used to compute the principal Hugoniot curve, and equilibrium thermodynamic quantities such as the specific heat, Grüneisen coefficient, and sound speed, are provided in the appendices.

Shock compression data for liquids. II. Condensed hydrogen and deuterium

Dynamic high pressure equation-of-state data are reported for liquid hydrogen and deuterium. Standard high explosive techniques were used to obtain the data from single and double shock compression. The shock velocity–particle velocity data on the principal Hugoniot curves are best fit by a quadratic expression in particle velocity. Intercepts of these expressions with the shock velocity axes agree very well with the measured sound speed. Over the pressure range studied, neither liquid exhibited a transition for the principal Hugoniot curves and no abnormal behavior was observed from the double-shock data. Theoretical Hugoniot curves for these liquids were computed using an equation of state from the Sesame library. The calculations agree with the measurements to within experimental error.

Longitudinal elastic velocities in MgO to 360 KB

Numerical descriptions of shock wave induced flows obtained with a two-dimensional Lagrangian finite difference code are compared in detail with experimental data obtained via the lateral relaxation method for polycrystalline magnesium oxide (MgO) to a pressure of 360 kbar. The equation of state used for MgO was assumed to be of the Mie-Gruneisen form, and detailed comparison of experimental and calculated data was used to obtain refined values of the shear strength and shear modulus of MgO at high pressures. The best fitting rheological model for MgO was characterized by a shear strength which decreased from a value of 26 kbar at 16.5-kbar mean stress to 13.5 kbar at 360-kbar mean stress along the principal Hugoniot curve. The first and second pressure derivatives of the shear modulus, when the shear modulus is evaluated as a quadratic function of pressure, yield (∂μ/∂P) = 2.44 and μ(∂^2μ/∂P^2) = 1.7±3.0. The uncertainties in the determination of μ(∂^2μ/∂P^2) have been reduced by a factor of 5 over previous estimates.