Screening effects in dense Coulomb media: Beyond the Poisson–Boltzmann and Kirkwood approximations

A theoretical approach is proposed that allows giving a suitable description of the equilibrium characteristics of dense heterogeneous Coulomb media, for example, dusty plasma (DP) and ionic colloidal suspensions containing charged particles (grains) of finite size. It is shown that taking into acco...

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Bibliographic Details
Published in:Physics of plasmas 2022-06, Vol.29 (6)
Main Authors: Bondarev, V. N., Dragan, G. S.
Format: Article
Language:English
Subjects:
Approximation
Barium oxides
Charged particles
Dimensionless numbers
Dusty plasmas
Electrolytes
Free energy
Ideal gas
Ionic crystals
Lithium fluoride
Parameters
Plasma physics
Screening
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Summary:A theoretical approach is proposed that allows giving a suitable description of the equilibrium characteristics of dense heterogeneous Coulomb media, for example, dusty plasma (DP) and ionic colloidal suspensions containing charged particles (grains) of finite size. It is shown that taking into account the Carnahan–Starling closed formula for the contribution of hard spheres of diameter d and number density n into the free energy of DP essentially improves the approximations by Poisson–Boltzmann (ideal gas of point ions) and Kirkwood (ideal gas of finite-sized ions). Thus, in systems like DP, along with the Kirkwood parameter (the ratio of d to the Debye–Hückel screening length), a second independent dimensionless parameter nd3 appears. As a result, for the first time, an opportunity opens up to give a natural explanation of the experimental fact, according to which the screening length in a concentrated electrolyte may turn out to be an increasing function of nd3. Useful evidence of the internal consistency of the theory is that it allows one to give a satisfactory numerical estimate of the dimensionless temperature of DP triple point (vapor–liquid–solid), in agreement with Monte Carlo simulations for concentrated electrolytes like CsCl. Furthermore, the results obtained are in quantitative agreement with a fairly wide set of experimental data on the melting of real ionic crystals (from LiF to CsI and from MgO to BaO) and, thus, provide a theoretical basis for the long-established empirical “similarity rule” that relates melting temperatures to effective ion sizes.
ISSN:1070-664X
1089-7674
DOI:10.1063/5.0089918