Fluid-fluid phase behaviour in the explicit solvent ionic model: hard spherocylinder solvent molecules
| Autor: | T. Patsahan, Oksana Patsahan, Myroslav Holovko, M. Hvozd |
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| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: |
Phase transition
Materials science Component (thermodynamics) FOS: Physical sciences Ionic bonding Thermodynamics 02 engineering and technology Hard spheres Condensed Matter - Soft Condensed Matter 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Atomic and Molecular Physics and Optics 0104 chemical sciences Electronic Optical and Magnetic Materials Ion Solvent Materials Chemistry Soft Condensed Matter (cond-mat.soft) Particle Molecule Physical and Theoretical Chemistry 0210 nano-technology Spectroscopy |
| Popis: | We study a fluid-fluid phase transition of the explicit solvent model represented as a mixture of the restricted primitive model (RPM) of ionic fluid and neutral hard spherocylinders (HSC). To this end, we combine two theoretical approaches, i.e., the scale particle theory (SPT) and the associative mean spherical approximation (AMSA). Whereas the SPT is sufficient to provide a rather good description of a reference system taking into account hard-core interactions, the AMSA is known to be efficient in treating the Coulomb interactions between the ions. Alternatively, we also use the mean spherical approximation (MSA) for comparison. In general, both approximations lead to similar qualitative results for the phase diagrams: the region of coexisting envelope becomes broader and shifts towards larger densities and higher temperatures when the pressure increases. However, the AMSA and the MSA produce different concentration dependences, i.e., contrary to the MSA, the AMSA phase diagrams show that the high-density phase mostly consists of the ions for all pressures considered. To demonstrate the effect of asphericity of solvent molecules on the fluid-fluid phase transition, we consider an "equivalent" mixture in which the HSC particles are replaced by hard spheres (HS) of the same volume. It is observed that in the case of HSC solvent (RPM-HSC model), the region of phase coexistence is wider than for the case of the solvent molecules being of spherical shape (RPM-HS model). It is also found that the critical temperature is higher in the RPM-HSC model than in the RPM-HS model, though it becomes the same at higher pressures in the MSA, while in the AMSA this difference remains essential. 18 pages |
| Databáze: | OpenAIRE |
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