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High fidelity equation of state for xenon : integrating experiments and first principles simulations in developing a wide-range equation of state model for a fifth-row element

Magyar, Rudolph J.; Root, Seth R.; Carpenter, John H.; Mattsson, Thomas M.

The noble gas xenon is a particularly interesting element. At standard pressure xenon is an fcc solid which melts at 161 K and then boils at 165 K, thus displaying a rather narrow liquid range on the phase diagram. On the other hand, under pressure the melting point is significantly higher: 3000 K at 30 GPa. Under shock compression, electronic excitations become important at 40 GPa. Finally, xenon forms stable molecules with fluorine (XeF{sub 2}) suggesting that the electronic structure is significantly more complex than expected for a noble gas. With these reasons in mind, we studied the xenon Hugoniot using DFT/QMD and validated the simulations with multi-Mbar shock compression experiments. The results show that existing equation of state models lack fidelity and so we developed a wide-range free-energy based equation of state using experimental data and results from first-principles simulations.

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TYPE Conference YEAR 2010
OSTI

As symmetric spreading in highly advective, disordered environments

Proposed for publication in Physical Review Letters.

Carpenter, John H.

Spreading of bacteria in a highly advective, disordered environment is examined. Predictions of super-diffusive spreading for a simplified reaction-diffusion equation are tested. Concentration profiles display anomalous growth and super-diffusive spreading. A perturbation analysis yields a crossover time between diffusive and super-diffusive behavior. The time's dependence on the convection velocity and disorder is tested. Like the simplified equation, the full linear reaction-diffusion equation displays super-diffusive spreading perpendicular to the convection. However, for mean positive growth rates the full nonlinear reaction-diffusion equation produces symmetric spreading with a Fisher wavefront, whereas net negative growth rates cause an asymmetry, with a slower wavefront velocity perpendicular to the convection.

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TYPE Journal Article YEAR 2005
OSTI
Results 51–65 of 65
Results 51–65 of 65