Hugoniot States and Mie–Grüneisen Equation of State of Iron Estimated Using Molecular Dynamics

The objective of this study was to develop a micromechanical approach for determining the Mie–Grüneisen EOS parameters of iron under the Hugoniot states. The multiscale shock technique (MSST) coupled with molecular dynamics (MD) simulations was employed to describe the shocked Hugoniot relation of single-crystal (SC) and nanocrystalline (NC) iron under high pressures. The Mie–Grüneisen equation of state (EOS) parameters, the cold pressure (Pc), the cold energy (Ec), the Grüneisen coefficient (γ), and the melting temperature (Tm) are discussed. The error between SC and NC iron results was found to be less than 1.5%. Interestingly, the differences in Hugoniot state (PH) and the internal energy between SC and NC iron were insignificant, which shows that the effect of grain size (GS) under high pressures was not significant. The Pc and Ec of SC and NC iron calculated based on the Morse potential were almost the same with those calculated based on the Born–Mayer potential; however, those calculated based on the Born–Mayer potential were a little larger at high pressures. In addition, several empirical and theoretical models were compared for the calculation of γ and Tm. The Mie–Grüneisen EOSs were shown on the 3D contour space; the pressure obtained with the Hugoniot curves as the reference was larger than that obtained with the cold curves as the reference.

Dynamic response of graphene and yttria-stabilized zirconia (YSZ) composites

A series of dynamic compaction studies were performed on yttria-stabilized zirconia (YSZ) and graphene composites using uniaxial flyer plate impact experiments. Studies aimed to characterize variation in dynamic behavior with respect to morphological differences for eight powdered YSZ and graphene compositions. Parameters of interest included YSZ particle size (nanometer or micrometer) and added graphene content (graphene weight percentage: 0%, 1%, 3%, 5%). Experiments were performed over impact velocities ranging between 315 and 586 m/s, resulting in pressures between 0.8 and 2.8 GPa. Hugoniot states measured appear to exhibit dependence on particle size and graphene content. Shock velocities tended to increase with graphene content and were generally larger in magnitude for the micrometer particle size YSZ. Compacted densities tended to increase as graphene content was increased and were generally larger in magnitude for the micrometer particle size YSZ samples. Resulting Hugoniot curves are compared and summarized to convey the dynamic behavior of the specimens.

Chapman-Jouguet Combustion Waves in Van Der Waals and Noble-Abel Gases

This chapter adopts the Chapman-Jouguet approach to derive jump conditions across combustion waves propagating in Van der Waals and Noble-Abel gases. The steady one-dimensional balance equations of mass, momentum and energy, assuming different properties of reactants and products, are applied to obtain the main properties of combustion waves, including velocities, Mach numbers, pressures and temperatures, in terms of the covolumes and intermolecular force parameters. In general, the effects of covolumes are more significant than the effects of the intermolecular attraction forces on Hugoniot curves and on properties of combustion waves. However, theoretical results using the Van der Waals equation of state matched more closely the experimental results for detonations of mixtures of propane and diluted air at high initial pressures.

Simulations of Shocked Methane Including Self-consistent Semiclassical Quantum Nuclear Effects

ABSTRACTA methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects on the fly. We introduce a modification of the multi-scale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new approach are found comparable with existing experimental data. We find that the self-consistent nature of the method results in the onset of chemistry at 40% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature change associated with quantum heat capacity is determined to be the primary factor in this shift.

Approaching the “cold curve” in laser-driven shock wave experiment of a matter precompressed by a partially perforated diamond anvil

This paper suggests a novel route to approach the cold compression curve in laser-plasma induced shock waves. This effect is achieved with a precompression in a diamond anvil cell (DAC). In order to keep the necessary structure of one dimensional shock wave it is required to use a diamond anvil cell with a partially perforated diamond anvil. Precompression pressures of about 50 GPa, that are an order of magnitude higher than the currently reported pressures, are possible to obtain with presentley existing diamond anvil cell technology. The precompressed Hugoniot of Al was calculated for different precompression pressures and it was found that at precompression pressure of 50 GPa the Hugoniot follows the “cold curve” up to about 2 Mbar and 5.2 g/cc. Furthermore, the thermal relative contribution on the Hugoniot curves is calculated.