Wide ranging equation of state with Tartarus: A hybrid Green’s function/orbital based average atom code

Starrett, C. E.; Gill, N. M.; Sjostrom, Travis; Greeff, C. W.

doi:10.1016/j.cpc.2018.10.002

Cited by 33 publications

(28 citation statements)

References 54 publications

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“…Here we will provide a brief overview of the model. For more details on the calculation, we defer the reader to reference [21]. The Tartarus average atom model consists of an atom in a sphere of volume V ion , where V ion is the average volume taken up by ions in the plasma.…”

Section: Calculation Details a Ground State Calculationmentioning

confidence: 99%

“…Average atom models are usually DFT-based models of atoms embedded in plasmas, and they have seen * ngill@lanl.gov widespread use in the study of thermodynamic quantities in dense plasmas (for example, see the following references [11,[19][20][21]). Most average atom models have the benefit of implicitly accounting for plasma density effects through the use of a finite-sized spherical cavity in which all of an ion's electrons and the nucleus are contained.…”

Section: Introductionmentioning

confidence: 99%

“…In this work we apply TD-DFT under the linear response formalism to study the opacity of an average atom. Our average atom model is calculated using the Tartarus code [21,28], and the linear response formalism of finite-temperature TD-DFT that we apply is similar to that implemented by Grimaldi et al [22]. The focus of our results is to study the opacity of plasmas at conditions relevant to the aforementioned Sandia experiments.…”

Section: Introductionmentioning

confidence: 99%

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Time-Dependent Density Functional Theory Applied to Average Atom Opacity

Gill,

Fontes,

Starrett

2021

Preprint

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We focus on studying the opacity of iron, chromium, and nickel plasmas at conditions relevant to experiments carried out at Sandia National Laboratories [J. E. Bailey et al., Nature 517, 56 (2015)]. We calculate the photo-absorption cross-sections and subsequent opacity for plasmas using linear response time-dependent density functional theory (TD-DFT). Our results indicate that the physics of channel mixing accounted for in linear response TD-DFT leads to an increase in the opacity in the bound-free quasi-continuum, where the Sandia experiments indicate that models under-predict iron opacity. However, the increase seen in our calculations is only in the range of 5-10%. Further, we do not see any change in this trend for chromium and nickel. This behavior indicates that channel mixing effects do not explain the trends in opacity observed in the Sandia experiments.

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Section: Calculation Details a Ground State Calculationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Time-Dependent Density Functional Theory Applied to Average Atom Opacity

Gill,

Fontes,

Starrett

2021

Preprint

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“…In comparison, average atom (AA) models are computationally far less demanding because they place only a single nucleus at the center of a cloud of electrons and determine the resulting states. Many variations of the AA approach exist [25,[31][32][33]. However, when these methods are applied to guide or interpret experiments at extreme densities or highly degenerate plasma conditions, the results appear to deviate from predictions of ab initio methods [26,[34][35][36], which provided the initial motivation for this study.…”

Section: Introductionmentioning

confidence: 99%

Reconciling ionization energies and band gaps of warm dense matter derived with ab initio simulations and average atom models

Massacrier,

Böhme,

Vorberger

et al. 2021

Preprint

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Average atom (AA) models allow one to efficiently compute electronic and optical properties of materials over a wide range of conditions and are often employed to interpret experimental data. However, at high pressure, predictions from AA models have been shown to disagree with results from ab initio computer simulations. Here we reconcile these deviations by developing an innovative type of AA model, AvIon, that computes the electronic eigenstates with novel boundary conditions within the ion sphere. Bound and free states are derived consistently. We drop the common AA image that the free-particle spectrum starts at the potential threshold, which we found to be incompatible with ab initio calculations. We perform ab initio simulations of crystalline and liquid carbon and aluminum over a wide range of densities and show that the computed band structure is in very good agreement with predictions from AvIon.

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“…Total pressures in Mbar for aluminum plasmas from the RSGF method, compared to KKR-GF results of reference[29], and to the Tartarus average atom model[34], as well as to a calculation with the multiple scattering Green's function set to zero (No MS). Also shown, beside the No MS and Tartarus columns are the percentage differences of that model's pressure compared to the RSGF result.…”

mentioning

confidence: 99%

Real-Space Green's functions for Warm Dense Matter

Laraia,

Hanson,

Shaffer

et al. 2021

Preprint

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Accurate modeling of the electronic structure of warm dense matter is a challenging problem whose solution would allow a better understanding of material properties like equation of state, opacity, and conductivity, with resulting applications from astrophysics to fusion energy research.Here we explore the real-space Green's function method as a technique for solving the Kohn-Sham density functional theory equations under warm dense matter conditions. We find the method to be tractable and accurate throughout the density and temperature range of interest, in contrast to other approaches. Good agreement on equation of state is found when comparing to other methods, where they are thought to be accurate.

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Wide ranging equation of state with Tartarus: A hybrid Green’s function/orbital based average atom code

Cited by 33 publications

References 54 publications

Time-Dependent Density Functional Theory Applied to Average Atom Opacity

Time-Dependent Density Functional Theory Applied to Average Atom Opacity

Reconciling ionization energies and band gaps of warm dense matter derived with ab initio simulations and average atom models

Real-Space Green's functions for Warm Dense Matter

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