Cold melting of beryllium: Atomistic view on Z-machine experiments

Dremov, V. V.; Rykounov, Alexey A.; Sapozhnikov, F.A.; Karavaev, A. V.; Yakovlev, S. V.; Ionov, G.V.; Ryzhkov, M. V.

doi:10.1063/1.4923430

Cited by 9 publications

(27 citation statements)

References 30 publications

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“…Our Hugoniot curve intersects the melting line at 235 GPa and 4900 K, consistent with previous theoretical works of dynamical loading by nonequilibrium molecular dynamics (NEMD), where amorphous [38] or recrystallized structures [29] form well below the equilibrium melting curve. These disordered structures could possibly explain the discrepancy of onset pressure of melt along Hugoniot in shock experiments (∼205 GPa) [9,30].…”

Section: Introductionsupporting

confidence: 90%

“…Various simulation methods have been applied to study the melting line of beryllium at high pressure and temperature. Both the heat-until-melt (HUM) [18] and the two-phase methods [8] have been used to predict the melting temperature of Be at high pressure, while the Modified Embedded Atom Model (MEAM) has been implemented to explore large-scale phenomena of melting under both hydrostatic and shock compression conditions [29]. Although it is often regarded as upper limit of melting temperature, HUM method gave consistent results with two-phase simulations [8,18].…”

Section: Introductionmentioning

confidence: 98%

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High Pressure Phase Diagram of Beryllium from \emph{Ab Initio} Free Energy Calculations

Wu,

Gonzalez,

Militzer

2021

Preprint

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We use first principles molecular dynamics simulations coupled to the thermodynamic integration method to study the hcp-bcc transition and melting of beryllium up to a pressure of 1600 GPa. We derive the melting line by equating solid and liquid Gibbs free energies, and represent it by a Simon Glatzel fit Tm = 1564 K(1+P/(15.6032 GPa)) 0.383 , which is in good agreement with previous two-phase simulations below 6000 K. We also derive the hcp-bcc solid-solid phase boundary and show the quasiharmonic approximation underestimates the stability of the hcp structure, predicting lower transition pressures between hcp and bcc phases. However, our results are consistent with the stability regime predicted by the phonon quasiparticle method. We also predict that hcp-bcc-liquid triple point is located at 164.7 GPa and 4314 K. In addition, we compute the shock Hugoniot curve, and show that it is in good agreement with experiments, intersecting our derived melting curve at ∼235 GPa at 4900 K. Finally, we show that an isentropic compression path that intersects the melting curve at both low and high temperature in the liquid regime, can reappear in the solid after a gap as large as 7000 K. Therefore, we predict that a large section of the melting curve could be sampled, in principle, by a ramp compression experiment, where solid and liquid Be would coexist as the sample is compressed.

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Section: Introductionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 98%

High Pressure Phase Diagram of Beryllium from \emph{Ab Initio} Free Energy Calculations

Wu,

Gonzalez,

Militzer

2021

Preprint

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“…The VM phenomenon in a shock wave was confirmed and further elaborated in MD simulations for single crystal Cu, Al, Ta, Pb in [46,151,441,443] and for polycrystalline Be in [84].…”

Section: Virtual Melting As a New Mechanism Of Plastic Deformation An...mentioning

confidence: 66%

“…Application of thermodynamic laws results, in particular, to the expressions ( 79) and (80) for the first Piola-Kirchhoff P P P and Cauchy σ σ σ stress tensor, which are presented in the general form and for elastic energy (76). Expressions ( 25)- (84) for dissipation rate due to plastic flow D p and variation of the internal variable D g , corresponding dissipative forces, the yield conditions and evolution equations for plastic strain and internal variables appear similar to those at small strain but using corresponding finite-strain measures. Specification for single crystals will be presented in Box 11.…”

Section: Finite Strain Formalismmentioning

confidence: 99%

Phase transformations, fracture, and other structural changes in inelastic materials

Levitas

2021

International Journal of Plasticity

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“…for lead 73 ) and 10 −4 sm -1 (e.g. for beryllium 74 ), and cannot be pushed far beyond this range by shock compression unless the loading is extreme (i.e. to several TPa 75 ).…”

Section: B Polycrystal Response Below the Helmentioning

confidence: 99%

Molecular dynamics simulations of grain interactions in shock-compressed highly textured columnar nanocrystals

Heighway

McGonegle

Park

et al. 2019

Phys. Rev. Materials

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While experimental and computational studies abound demonstrating the diverse range of phenomena caused by grain interactions under quasistatic loading conditions, far less attention has been given to these interactions under the comparatively dramatic conditions of shock compression. The consideration of grain interactions is essential within the context of contemporary shock-compression experiments that exploit the distinctive x-ray diffraction patterns of highly textured (and therefore strongly anisotropic) targets in order to interrogate local structural evolution. We present here a study of grain interaction effects in shock-compressed, body-centered cubic tantalum nanocrystals characterized by a columnar geometry and a strong fiber texture using large-scale molecular dynamics simulations. Our study reveals that contiguous grains deform cooperatively in directions perpendicular to the shock, driven by the gigapascal-scale stress gradients induced over their boundaries by the uniaxial compression, and in so doing are able to reach a state of reduced transverse shear stress. We compare the extent of this relaxation for two different columnar geometries (distinguished by their square or hexagonal cross-sections), and quantify the attendant change in the transverse elastic strains. We further show that cooperative deformation is able to replace ordinary plastic deformation mechanisms at lower shock pressures, and, under certain conditions, activate new mechanisms at higher pressures.

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Cold melting of beryllium: Atomistic view on Z-machine experiments

Cited by 9 publications

References 30 publications

High Pressure Phase Diagram of Beryllium from \emph{Ab Initio} Free Energy Calculations

High Pressure Phase Diagram of Beryllium from \emph{Ab Initio} Free Energy Calculations

Phase transformations, fracture, and other structural changes in inelastic materials

Molecular dynamics simulations of grain interactions in shock-compressed highly textured columnar nanocrystals

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