Mean-field treatment of polarons in strong electrolytes.

Using variational estimates for the grand partition function, we have developed a microscopic theory of an excess electron in an ionic liquid at high ion concentrations. We have derived the free-energy functional for the electron and have calculated electron energies for the ground and the first excited states as well as electron-ion correlation functions versus thermodynamic parameters of liquid and parameters of electron-ion potentials. We have found that the energetic characteristics of solvated electron are mainly determined by the Coulomb interaction which gives birth to polaronlike states, while ion cores have a pronounced quantitative effect on these characteristics. The local solvent structure around the excess electron is determined by the mean field induced by ions. Using the method developed we have calculated polaron characteristics in molten salts, such as the maximum of the absorption spectrum and its variations caused by changes in temperature, density, and composition of the electrolyte. The data obtained are in agreement with experiments and computer simulations.