Test of a theoretical equation of state for elemental solids and liquids

Chisolm, Eric D.; Crockett, Scott; Wallace, Duane C.

doi:10.1103/physrevb.68.104103

Cited by 55 publications

(43 citation statements)

References 26 publications

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“…3. We also show the Hugoniot curve as obtained by Chisholm et al [5] from analysis of experimental data and from first principle calculations. Fitting our results of simulations with defect-free aluminum samples gives the dashed curve.…”

Section: Dynamic Strength Of Metals In Shock Deformationmentioning

confidence: 83%

“…4 plotted as a function of the pressure p, both evaluated over the same region of the sample and the same time. Using the established equation of state for aluminum [5], the adiabatic temperature rise is as shown by the dotted curve. It does not account for the temperature increase generated by plastic deformation, which is of course included in our molecular dynamic simulations.…”

Section: Dynamic Strength Of Metals In Shock Deformationmentioning

confidence: 99%

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Dynamic strength of metals in shock deformation

Kubota

Reisman

Wolfer

2006

Applied Physics Letters

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It is shown that the Hugoniot and the critical shear stress required to deform a metal plastically in shock compression can be obtained directly from molecular dynamics simulations without recourse to surface velocity profiles, or to details of the dislocation evolution. Specific calculations are shown for aluminum shocked along the [100] direction, and containing an initial distribution of microscopic defects. The presence of such defects has a minor effect on the Hugoniot and on the dynamic strength at high pressures. Computed results agree with experimental data.Introduction.-The carriers of plastic deformation in crystalline solids are dislocations. To set them in motion requires shear stresses above a critical value, called the yield or plastic flow strength, or strength for short. It depends on the type of crystal, its orientation with respect to the applied forces, on the temperature, on any previous plastic deformation, and above all on the rate of deformation enforced by the applied forces. In general, the strength increases as the rate of deformation increases. To explore strength at extreme plastic strain rates of 10 4 and beyond, dynamic forces must be applied by impact of solids, by chemical explosives, pulsed magnetic fields, or laser ablation. The rapid application of these extreme forces induce shock waves that propagate from the impacted surface through the material at speeds on the order of the sound velocity, typically several km/s. Compression of the material and the ensuing plastic flow occur behind the shock front [1]. When the shock reaches the exit surface, its velocity can be measured as a function of time, and from the analysis of this velocity profile, the degree of compression or the density, the pressure, and the dynamic strength can be inferred. However, direct measurements of all three parameters behind the shock front are not possible.It has therefore been a goal for many years to employ atomistic simulations and study strong shock waves in solids, visualize the dynamic processes during shock compression and deformation, and also "measure", as it were, the thermodynamic field variables such as temperature, density, pressure, flow velocities, and stresses. Holian, one of the prominent pioneers in this field, has reviewed the historical development and the remaining challenges to reach this goal [2]. While the molecular dynamic simulations have provided numerous visualizations of dynamic dislocation behavior during shock compression, the complete set of thermodynamic field variables has so far not been obtained.Here, we give a brief account of having accomplished this last step, namely a complete mapping of the spatial and temporal distributions of all the thermodynamic variables: temperature, stresses and their rates, strains and their rates, as well as derivative parameters such as pressure, density, von Mises stress, and plastic strain and strain rates. Counting all components of tensors, this is a total of 40 distribution functions. With this information in hand, it is now possi...

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Section: Dynamic Strength Of Metals In Shock Deformationmentioning

confidence: 83%

Section: Dynamic Strength Of Metals In Shock Deformationmentioning

confidence: 99%

Dynamic strength of metals in shock deformation

Kubota

Reisman

Wolfer

2006

Applied Physics Letters

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“…As demonstrated in numerous classical and DFT-MD investigations on the EOS of liquids [9,54,[65][66][67], the equation of state of a monatomic liquid in the neighborhood of its melt curve is strikingly similar to that of a solid, in the sense that its specific heat at constant V is very nearly independent of V and is equal to ∼3k B /atom. Indeed, we observed this for C in our earlier work, even for temperatures up to twice T melt over a wide range of compressions [9,68].…”

Section: B Liquid Phasementioning

confidence: 98%

Multiphase equation of state for carbon addressing high pressures and temperatures

et al. 2014

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We present a 5-phase equation of state for elemental carbon which addresses a wide range of density and temperature conditions: 3g/cc < ρ < 20g/cc, 0 K < T < ∞. The phases considered are diamond, BC8, simple cubic, simple hexagonal, and the liquid/plasma state. The solid phase free energies are constrained by density functional theory (DFT) calculations. Vibrational contributions to the free energy of each solid phase are treated within the quasiharmonic framework. The liquid free energy model is constrained by fitting to a combination of DFT molecular dynamics performed over the range 10 000 K < T < 100 000 K, and path integral quantum Monte Carlo calculations for T > 100 000 K (both for ρ between 3 and 12 g/cc, with select higher-ρ DFT calculations as well). The liquid free energy model includes an atom-in-jellium approach to account for the effects of ionization due to temperature and pressure in the plasma state, and an ion-thermal model which includes the approach to the ideal gas limit. The precise manner in which the ideal gas limit is reached is greatly constrained by both the highest-temperature DFT data and the path integral data, forcing us to discard an ion-thermal model we had used previously in favor of a new one. Predictions are made for the principal Hugoniot and the room-temperature isotherm, and comparisons are made to recent experimental results.

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“…The 6061 alloy is less dense than aluminum 1100 and demonstrates a slightly stronger shock response 5 . While previous EOS for aluminum have been constructed [6][7][8] , none provide the high pressure solid phases, or have had access to the broad range of high accuracy simulations we have performed to constrain particularly the liquid state. However, several recent EOS have been constructed for different materials which are both multiphase and inclusive of the warm dense matter regime, and have also highly relied on simulation data [9][10][11] .…”

Section: Introductionmentioning

confidence: 99%

Multiphase aluminum equations of state via density functional theory

2016

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We have performed density functional theory (DFT) based calculations for aluminum in extreme conditions of both pressure and temperature, up to 5 times compressed ambient density and over 1 000 000 K in temperature. In order to cover such a domain, DFT methods including phonon calculations, quantum molecular dynamics, and orbital-free DFT are employed. The results are then used to construct a SESAME equation of state for the aluminum 1100 alloy, encompassing the fcc, hcp and bcc solid phases as well as the liquid regime. We provide extensive comparison with experiment and based on this we also provide a slightly modified equation of state for the aluminum 6061 alloy.

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Test of a theoretical equation of state for elemental solids and liquids

Cited by 55 publications

References 26 publications

Dynamic strength of metals in shock deformation

Dynamic strength of metals in shock deformation

Multiphase equation of state for carbon addressing high pressures and temperatures

Multiphase aluminum equations of state via density functional theory

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