Monte Carlo simulations of ionization potential depression in dense plasmas

Abstract

A particle-particle grand canonical Monte Carlo model with Coulomb pair potential interaction was used to simulate modification of ionization potentials by electrostatic microfields. The Barnes-Hut tree algorithm [J. Barnes and P. Hut, Nature 324, 446 (1986)] was used to speed up calculations of electric potential. Atomic levels were approximated to be independent of the microfields as was assumed in the original paper by Ecker and Kröll [Phys. Fluids 6, 62 (1963)]; however, the available levels were limited by the corresponding mean inter-particle distance. The code was tested on hydrogen and dense aluminum plasmas. The amount of depression was up to 50% higher in the Debye-Hückel regime for hydrogen plasmas, in the high density limit, reasonable agreement was found with the Ecker-Kröll model for hydrogen plasmas and with the Stewart-Pyatt model [J. Stewart and K. Pyatt, Jr., Astrophys. J. 144, 1203 (1966)] for aluminum plasmas. Our 3D code is an improvement over the spherically symmetric simplifications of the Ecker-Kröll and Stewart-Pyatt models and is also not limited to high atomic numbers as is the underlying Thomas-Fermi model used in the Stewart-Pyatt model.

Ionization-potential depression and dynamical structure factor in dense plasmas

“…The approach, presented in this work, shows a close connection of the IPD to the detailed structure of the plasma system. The general expression (13) with (14) should work within the valid range of the fluctuationdissipation theorem for both equilibrium and nonequilibrium systems described by the static SF of the quantum many-body system. Once the SF is known from other methods, for instance, simulations or Thomson scattering measurements, the IPD can be directly evaluated.…”

“…A critical discussion of these approaches and their applicability for the experiments given above was presented in [11]. Other approaches use Hartree-Fock-Slater calculations [12], Monte Carlo simulations [13], molecular dynamics simulations [14], density-functional theory calculations [15], microfield concepts and a detailed configuration accounting description [17,18], or the theory of disordered solids where itinerant band electrons become localized below a mobility edge [19].…”

Screening potential and continuum lowering in a dense plasma under solar-interior conditions

“…Comparisons of theoretical predictions with recent experiments have further revealed that the analytical models (Stewart & Pyatt 1966;Ecker & Kröll 1963;Rozsnyai 1972;Debye & Hückel 1923) have difficulty in capturing the essential features of hot, dense plasmas at solid and abovesolid densities. This lack of a consistent theoretical formulation for the IPD of hot dense plasmas has stimulated a variety of theoretical investigations (Preston et al 2013;Iglesias 2014;Hansen et al 2014;Crowley 2014;Son et al 2014;Calisti et al 2015;Vinko et al 2014;Stransky 2016;Lin et al 2017;Rosmej 2018;Kasim et al 2018;Ali et al 2018;Hu 2017;Röpke et al 2019;Kraus et al 2018).…”

Transient ionization potential depression in nonthermal dense plasmas at high x-ray intensity

“…To describe this IPD effect, two distinct models have been available, Ecker-Kröll (EK) [23] and Stewart-Pyatt (SP) [24], both of which are based on thermal equilibrium. Recent experiments using an XFEL [12,25] and a high-power optical laser [26,27] have triggered a controversial debate on the validity of these models, which has been followed by extensive studies on the IPD measurements [28][29][30][31][32][33] and the theoretical treatments of the IPD effect [34][35][36][37][38][39][40][41][42][43], including ab initio electronic structure calculations [44][45][46][47][48][49]. It is worthwhile to note that all of the employed methods are based on the LTE condition for the electronic subsystem.…”