Short- and long-range contributions to equilibrium and transport properties of solid electrolytes

Abstract

Condensed ionic systems are described in the framework of a combined approach that takes into account both long-range and short-range interactions. Short-range interaction is expressed in terms of mean potentials and long-range interaction is considered in terms of screening potentials. A system of integral equations for these potentials is constructed based on the condition of the best agreement of the system of study with the reference system. In contrast to the description of media with short-range interactions, in this text the reference distribution includes not only the field of mean potentials but also Coulomb interaction between particles. A one-component system made of ions in a neutralizing background of fixed counterions is considered. The model can be used to describe solid ionic conductors. In order to study the movement of cations on the sites of their sub-lattice, the lattice approximation of the theory is employed based on the calculation of the pair distribution function. Using the collective variables approach, a technique improving the starting expression for this function is proposed. Notably, the neglected terms in the expansion of this function are approximated by single-particle terms ensuring that the normalization condition is satisfied. As a result, the applicability of the theory is extended to a wide region of thermodynamic parameters. The chemical potential and the diffusion coefficient are calculated showing the possibility of phase transitions characteristic of the system.

Charge and electric field distributions in the interelectrode region of an inhomogeneous solid electrolyte

“…In contrast to our previous work [23], here we consider the case of an inhomogeneous system characterized by an inhomogeneous distribution of the density field. To model such a distribution, we take the mean occupation number to be different and extend the number of possible occupation numbers by describing the systems in terms of quasiparticles.…”

“…Solid ionic systems with conductivity induced by ions of the same sign [23] are characterized by short-range Van der Waals attraction and long-range Coulomb repulsion. They can also be viewed as systems interacting via a so-called SALR (short-range attractive and long-range repulsive) potential [24][25][26][27][28].…”

“…As a result, the energy of short-range Van der Waals interaction is comparable to the energy of Coulomb interaction [4][5][6][7][8]. To address this fact, we combine two methods that had previously been used to describe systems of neutral and charged particles, namely the methods used in [23,[29][30][31][32][33] with the collective variables approach capable of taking into account long-range interactions [20,21].…”

“…In our previous paper [23], the homogeneous case was considered. Such a case appears in the absence of an electric field when local charge compensation takes place.…”

“…To describe the solid nature of the objects under study, the partition function is expanded with respect to mean potentials [29,30]. The approach [23] applied to homogeneous systems here is extended to inhomogeneous states emerging under an external field induced by the electrodes. In the present work the results [32,33] are generalized by taking into account the effect of correlations.…”