Isochoric, isobaric, and ultrafast conductivities of aluminum, lithium, and carbon in the warm dense matter regime

Dharma‐wardana, M. W. C.; Klug, D. D.; Harbour, L.; Lewis, Laurent J.

doi:10.1103/physreve.96.053206

Cited by 24 publications

(47 citation statements)

References 69 publications

(172 reference statements)

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“…As the NPA + MHNC approach used by the present author has been described in many publications and recent papers, for example, we do not provide a discussion here. Instead, an account is given in Appendix for the convenience of the reader and for clarifying misconceptions found in the literature about the nature of the mean ionization Z .…”

Section: The Neutral Pseudo‐atom Model (Npa) In the Context Of Complesupporting

confidence: 75%

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Theory of complex fluids in the warm dense matter regime and application to an unusual phase transition in liquid carbon

Dharma‐wardana

2018

Contributions to Plasma Physics

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Data from recent laser‐shock experiments or from simulations using density functional theory (DFT), molecular dynamics (MD), path integrals etc. that are available for warm dense carbon are compared with the corresponding results predicted using the neutral pseudo‐atom [NPA] method. The NPA results are in good agreement not only with the 3–12 g/cm3 regimes that have been studied via path‐integral Monte Carlo methods but even at low densities and low temperatures where transient covalent bonding dominates ionic correlations. Thus, the “prepeak” due to the C–C bond at ∼1.4 Å and other features found in the pair distribution function g[r] from DFT + MD simulations at 0.86 eV and 3.7 g/cm3 and other densities etc. are recovered accurately in the NPA + HNC (hypernetted‐chain) calculations. The exploration of regimes not covered by previous studies is presented together with evidence of an unusual phase transition of carbon in the liquid state to a vapour, as seen from the loss of ion–ion correlations. An abrupt decrease in the number of free electrons per ion occurs simultaneously. A metallic liquid with strong ionic correlations arising from transient C–C bonds becomes a metallic vapour. This occurs when carbon at the density of ∼1.0 g/cm3 and mean ionization Z = 4 transits abruptly to a disordered mono‐atomic vapour at 7 eV, with Z ≃ 3. The behaviour of the pressure, compressibility and the electrical conductivity as well as physical quantities available from X‐ray Thomson scattering are presented across the tentatively proposed phase transition.

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Section: The Neutral Pseudo‐atom Model (Npa) In the Context Of Complesupporting

confidence: 75%

“…The MHNC‐generated g ( r ) are not limited by the size of the simulation box, and the Fourier transform S ( k ) for essentially all‐ k , including the k → 0 limit, and interaction potentials are readily available for rapid accurate calculations of the EOS and transport properties …”

Section: The Neutral Pseudo‐atom Model (Npa) In the Context Of Complementioning

confidence: 77%

Theory of complex fluids in the warm dense matter regime and application to an unusual phase transition in liquid carbon

Dharma‐wardana

2018

Contributions to Plasma Physics

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“…There is even less of a change at the higher density of 5.2 g/cm 3 used by Rüter et al [11], as the Fermi energy is correspondingly higher. The value ofZ for Al begins to increase only from about 20 eV, and the consistency of the NPA evaluatedZ even at higher temperatures is shown from its successful prediction of electrical conductivities of aluminum under a variety of WDM conditions [23,39].…”

Section: Resultsmentioning

confidence: 83%

Ion-ion dynamic structure factor, acoustic modes, and equation of state of two-temperature warm dense aluminum

et al. 2018

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The ion-ion dynamical structure factor and the equation of state of warm dense aluminum in a two-temperature quasiequilibrium state, with the electron temperature higher than the ion temperature, are investigated using molecular-dynamics simulations based on ion-ion pair potentials constructed from a neutral pseudoatom model. Such pair potentials based on density functional theory are parameter-free and depend directly on the electron temperature and indirectly on the ion temperature, enabling efficient computation of two-temperature properties. Comparison with ab initio simulations and with other average-atom calculations for equilibrium aluminum shows good agreement, justifying a study of quasiequilibrium situations. Analyzing the van Hove function, we find that ion-ion correlations vanish in a time significantly smaller than the electron-ion relaxation time so that dynamical properties have a physical meaning for the quasiequilibrium state. A significant increase in the speed of sound is predicted from the modification of the dispersion relation of the ion acoustic mode as the electron temperature is increased. The two-temperature equation of state including the free energy, internal energy, and pressure is also presented.

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“…Recently, Dharma-wardana [1] and Dharma-wardana et al [2] (both referred to as DWD in what follows) argued that the neutral pseudoatom (NPA) model can be applied to study matter isochorically heated by intense x-ray radiation to two-temperature states in strong nonequilibrium (ultra-fast matter: UFM). As a consequence a very low conductivity has been predicted to interpret the experiment [3].…”

mentioning

confidence: 99%

“…In Born approximation where the scattering cross section is replaced by |U ei (q)/ (q)| 2 , the familiar form of the Ziman formula (Ref. [2], Eq. (A14)) is obtained.…”

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confidence: 99%

Comment on “Isochoric, isobaric, and ultrafast conductivities of aluminum, lithium, and carbon in the warm dense matter regime”

et al. 2019

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Dharma-wardana et al. [M. W. C. Dharma-wardana et al., Phys. Rev. E 96, 053206 (2017)] recently calculated dynamic electrical conductivities for warm dense matter as well as for nonequilibrium two-temperature states termed "ultrafast matter" (UFM) [M. W. C. Dharma-wardana, Phys. Rev. E 93, 063205 (2016)]. In this comment we present two evident reasons, why these UFM calculations are neither suited to calculate dynamic conductivities nor x-ray Thomson scattering spectra in isochorically heated warm dense aluminum. First, the ion-ion structure factor, a major input into the conductivity and scattering spectra calculations, deviates strongly from that of isochorically heated aluminum. Second, the dynamic conductivity does not show a non-Drude behavior which is an essential prerequisite for a correct description of the absorption behavior in aluminum. Additionally, we clarify misinterpretations by Dharma-wardana et al. concerning the conductivity measurements of Gathers [

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Isochoric, isobaric, and ultrafast conductivities of aluminum, lithium, and carbon in the warm dense matter regime

Cited by 24 publications

References 69 publications

Theory of complex fluids in the warm dense matter regime and application to an unusual phase transition in liquid carbon

Theory of complex fluids in the warm dense matter regime and application to an unusual phase transition in liquid carbon

Ion-ion dynamic structure factor, acoustic modes, and equation of state of two-temperature warm dense aluminum

Comment on “Isochoric, isobaric, and ultrafast conductivities of aluminum, lithium, and carbon in the warm dense matter regime”

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