Thermodynamic properties and the plasma phase transition of dense helium plasma

“…The question of a plasma phase transition in pure helium was investigated much less, [24,251. As in the case of hydrogen, a plasma phase transition is predicted for dense helium too.…”

Section: Introductionmentioning

confidence: 99%

Plasma Phase Transition in Fluid Hydrogen‐Helium Mixtures

Schlanges

Bönitz

Tschttschjan

1995

Contrib. Plasma Phys.

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“…The formation of bound state is reflected by shoulders and minima of the relative pressure. The agreement with earlier calculations of the pressure using the mass action law [ 1,12,13 ] is, in particular around the minimum, not yet satisfactory. However, we see that the main effects, the formation of atoms and molecules and their destruction at very high densities, are correctly described.…”

Section: Combination Of Screening and Bound State Effects In Dense Pl...contrasting

confidence: 50%

“…In the higher approximations, the ionic contribution may be approximated at high densities by Wigner‐type expansions. [ 26,28,46 ] In the density region, which we will study here, we may use for

y_{i} = n_{i} {(Z_{i}^{2} e^{2} false/ k_{B} T)}^{3} > > 1

, an analytical approximation for the ionic pressure stemming from an interpolation of Monte Carlo calculations [ 12,13,28,46 ] :

p_{i}^{normalWi} false[normalRy false] ≃ - n_{i} k_{B} T false(0.0599 y_{i}^{- 1 / 12} + 0.3180 + 0.3578 y_{i}^{1 / 12} + 0.4825 y_{i}^{1 / 3} false) .

For the ionic fugacities we have at high densities correspondingly, see Sect. 6.5. in [ 28 ] :

z_{i}^{normalWi} = n_{i} \exp false[- false(1.9228 y_{i}^{1 / 3} - 2.3922 y_{i}^{1 / 12} + 0.16708 \ln false(y_{i} false) + 3.215 false) false]

\times \exp [- \frac{r_{s}}{(1 + r_{s}^{2})} false(0.0736 y_{i}^{1 / 3} + 0.6328 y_{i}^{- 1 / 12} - 0.1779 false)] .

In contrast to the situation at small densities, the contribution of the bound states is in the high‐density region just a perturbation that sometimes may be neglected in the limit of very high densities and pressures.…”

Section: Equation Of State At High Densities and Pressuresmentioning

confidence: 99%

“…For full thermal ionization, for example, of all helium electrons, we need energies of far more than 100 eV, that is temperatures more than 10 6 K. Alternatively, high ionization degrees can be reached by increasing the particle density to the regions of

n > 10^{23}

cm −3 where all atomic and molecular bound states are destroyed by screening and Pauli blocking effects (pressure ionization). [ 8–16 ]…”

Section: Introductionmentioning

confidence: 99%

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Equation of state of hydrogen, helium, and solar plasmas

Ébeling

Reinholz

Röpke

2021

Contributions to Plasma Physics

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The equation of state (EOS) for plasmas of the two lightest elements H and He, and mixtures as typical for the plasmas in the sun are calculated. The contributions of deep bound states are included by using inverted fugacity expansions. The inversion of fugacities to densities is reduced to solvable algebraic problems and expressed by rational polynomials. The calculation of relative pressures is carried out separately for low and high densities. Near the crossing point, in between, the separate solutions are connected to each other by smooth concatenation. Applications to hydrogen–helium plasmas in the sun including estimates for the isentropic EOS are discussed.

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