Density-functional calculation of the Hugoniot of shocked liquid deuterium (original) (raw)
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Density-Functional Molecular Dynamics Simulations of Shocked Molecular Liquids
2001
Molecular dynamics (MD) simulations have been performed for highly compressed fluid deuterium, nitrogen, and oxygen, in the density and temperature regime of shock-compression experiments, using density functional (DF) electronic structure techniques to describe the interatomic forces. The Hugoniots derived from the calculated equation-of-state for deuterium does not exhibit the large compression predicted by the recently reported laser-driven experiments. However, the Hugoniot derived for nitrogen and oxygen agree well with explosively-driven and gas-gun experiments. The nature of the fluid along the Hugoniot, as calculated with DF-MD, has been analyzed. All three species (D2, N2, and C^) undergo a continuous transition from a molecular to a partially dissociated fluid containing a mixture of atoms and molecules.
Physics of Plasmas, 2015
We present computational results and tables of the equation-of-state, thermodynamic properties, and shock Hugoniot for hot dense fluid deuterium. The present results are generated using a recently developed chemical model that takes into account different high density effects such as Coulomb interactions among charged particles, partial degeneracy, and intensive short range hard core repulsion. Internal partition functions are evaluated in a statisticalmechanically consistent way implementing recent developments in the literature. The shock Hugoniot curve derived from the present tables is in reasonable overall agreement with the Hugoniot derived from the Nova-laser shock wave experiments on liquid deuterium, showing that deuterium has a significantly higher compressibility than predicted by the SESAME tables or by Path Integral Monte Carlo (PIMC) calculations. Computational results are presented as surface plots for the dissociated fraction, degree of ionization, pressure, and specific internal energy for densities ranging from 0.0001 to 40 g/cm 3 and temperatures from 2000 to ~ 10 6 K. Tables for values of the above mentioned quantities in addition to the specific heat at constant pressure, c p , ratio of specific heats, c p /c v , sound speed and Hugoniot curve (for a specific initial state) are presented for practical use.
Quantum Molecular Dynamics Simulations of Shocked Molecular Liquids
Nucleation and Atmospheric Aerosols, 2004
Using quantum molecular dynamics, we study the dissociation of nitrogen oxide along the principal and reshocked Hugoniots. We obtain good agreement with available experimental data for the first and highest second-shock Hugoniots. Reminiscent of the experimental and theoretical findings for shocked liquid nitrogen, the calculation indicates little temperature variation along the second shock as the fluid dissociates. The analysis of the concentration of molecular species along both Hugoniots indicates, as expected, that for low final shock densities molecular nitrogen is forming when nitrogen oxide dissociates. In contrast to basic assumptions used for high pressure modeling of nitrogen oxide, we find, however, that oxygen mostly stays in an atomic state for the whole density-temperature range studied.
Calculation of a Deuterium Double Shock Hugoniot from Ab Initio Simulations
Physical Review Letters, 2001
We calculate the equation of state of dense deuterium with two ab initio simulations techniques, path integral Monte Carlo and density functional theory molecular dynamics, in the density range of 0.67 ≤ ρ ≤ 1.60 g cm −3 . We derive the double shock Hugoniot and compare with the recent laser-driven double shock wave experiments by Mostovych et al. . We find excellent agreement between the two types of microscopic simulations but a significant discrepancy with the laser-driven shock measurements.
Monte Carlo calculations of thermodynamic properties of deuterium under high pressures
Journal of Physics: Conference Series, 2008
Two different numerical approaches have been applied for calculations of shock Hugoniots and compression isentrope of deuterium: direct path integral Monte Carlo and reactive Monte Carlo. The results show good agreement between two methods at intermediate pressure which is an indication of correct accounting of dissociation effects in the direct path integral Monte Carlo method. Experimental data on both shock and quasi-isentropic compression of deuterium are well described by calculations. Thus dissociation of deuterium molecules in these experiments together with interparticle interaction play significant role.
Shock wave propagation in dissociating low-Z liquids: D2
The Journal of Chemical Physics, 2005
We present direct molecular dynamics simulations of shock wave propagation in liquid deuterium for a wide range of impact velocities. The calculated Hugoniot is in perfect agreement with the gas-gun data as well as with the most recent experimental data. At high impact velocities we observe a smearing of the shock wave front and propagation of fast dissociated molecules well ahead of the compressed region. This smearing occurs due to the fast deuterium dissociation at the shock wave front. The experimental results are discussed in view of this effect.
The shock wave structure in nitrogen is studied by solving the Boltzmann kinetic equation generalized for polyatomic gases with internal degrees of freedom. The collision operator is evaluated by the method proposed in [1, 2] that ensures strict conservation of mass, impulse and energy and gives equilibrium rotational spectrum at the thermodynamic equilibrium conditions. Detailed distributions of gas density, translational and rotational temperatures are presented together with populations of the rotational levels at several characteristic points along the shock wave front. Non-equilibrium rotational spectrum is obtained inside the shock wave. Results of simulations are compared to experimental data and simulation results of other authors obtained by Monte Carlo methods FIGURE 3. Shock wave structure (left) and rotational spectra at different points along the shock wave (right) in Nitrogen at M=12.9.
Novel Simulations of Energetic Materials: Circumventing Limitations in Existing Methodologies
Transformational Science and Technology for the Current and Future Force - Proceedings of the 24th US Army Science Conference, 2006
We present a methodology for the efficient calculation of the shock Hugoniot using standard molecular simulation techniques. The method is an extension of an equation of state methodology proposed by Erpenbeck [J. J. Erpenbeck, Phys. Rev. A 46, 6406 (1992)] and is considered as an alternative to other methods that generate Hugoniot properties. We illustrate the methodology for shocked liquid N 2 using two different simulation methods: (a) the Reaction Ensemble Monte Carlo method for a reactive system; and (b) the molecular dynamics method for a non-reactive system. The method is shown to be accurate, stable and generally independent of the algorithm parameters. We find excellent agreement with results calculated by other previous simulation studies. The results show that the methodology provides a simulation tool capable of determining points on the shock Hugoniot from a single simulation in an efficient, straightforward manner.