A study of the electronic and ionic structure, for competing states of fully and partially ionized hydrogen, using the neutral pseudo-atom method as well as a classical map for the electron subsystem
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arXiv
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| Format: | Preprint |
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2025
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| author | Dharma-wardana, M. W. C. |
| author_facet | Dharma-wardana, M. W. C. |
| contents | Prof. Bonitz and his collaborators have made seminal contributions to the study of the uniform electron fluid and the electron-proton fluid, viz., hydrogen, in using {\it ab initio} simulations, as reflected in this festschrift. Here we review the theoretical methods available for these systems where traditional small-parameter methods fail. We use the neutral-pseudo atom (NPA) method, and a classical map for quantum electrons to study hydrogen plasmas. We show that {\it both} fully-ionized and partially-ionized hydrogen phases can exist with the same nominal density and temperature, at pressures and temperatures of interest to planetary physics. The mean ionization $\bar{Z}$, pair-distribution functions, free energies, pressures and conductivities are calculated for the competing phases. Here $\bar{Z}$ is also a measure of the miscibility of fully ionized and un-ionized hydrogen. Recent studies using path-integral Monte Carlo methods, and $N$-atom Density Functional Theory (DFT) simulations have provided essential structure data including the electron-electron structure factor $S_{ee}(k)$ that enters into interpretation of X-ray Thomson scattering and other diagnostics. We show that these structure data can be inexpensively evaluated using classical-map schemes for fully ionized plasmas, and more generally, using one-atom (average-atom) DFT methods for partially ionized systems. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_00388 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | A study of the electronic and ionic structure, for competing states of fully and partially ionized hydrogen, using the neutral pseudo-atom method as well as a classical map for the electron subsystem Dharma-wardana, M. W. C. Plasma Physics Statistical Mechanics Prof. Bonitz and his collaborators have made seminal contributions to the study of the uniform electron fluid and the electron-proton fluid, viz., hydrogen, in using {\it ab initio} simulations, as reflected in this festschrift. Here we review the theoretical methods available for these systems where traditional small-parameter methods fail. We use the neutral-pseudo atom (NPA) method, and a classical map for quantum electrons to study hydrogen plasmas. We show that {\it both} fully-ionized and partially-ionized hydrogen phases can exist with the same nominal density and temperature, at pressures and temperatures of interest to planetary physics. The mean ionization $\bar{Z}$, pair-distribution functions, free energies, pressures and conductivities are calculated for the competing phases. Here $\bar{Z}$ is also a measure of the miscibility of fully ionized and un-ionized hydrogen. Recent studies using path-integral Monte Carlo methods, and $N$-atom Density Functional Theory (DFT) simulations have provided essential structure data including the electron-electron structure factor $S_{ee}(k)$ that enters into interpretation of X-ray Thomson scattering and other diagnostics. We show that these structure data can be inexpensively evaluated using classical-map schemes for fully ionized plasmas, and more generally, using one-atom (average-atom) DFT methods for partially ionized systems. |
| title | A study of the electronic and ionic structure, for competing states of fully and partially ionized hydrogen, using the neutral pseudo-atom method as well as a classical map for the electron subsystem |
| topic | Plasma Physics Statistical Mechanics |
| url | https://arxiv.org/abs/2510.00388 |