| Using path integrals and the theory of polarizable fluids, I develop a model to treat fluctuation induced forces between electrons solvated in metal-ammonia solutions (MAS). I have argued that at finite metal concentrations, the collective behavior of the solvated electrons is controlled by these interactions. I evaluate dielectric, optical, and thermodynamical properties of MAS. These properties are found to be mainly determined by the fluctuation-induced forces, which result in the two main effects: the dispersion attractions between the electrons and a sharp increase in the static dielectric constant of the solution. The first effect creates a classical phase separation for the light alkali metal solutes below a critical temperature. The second effect leads to a peculiar nonmetal-metal transition, which appears as a sharp dielectric enhancement and a mechanical instability of the system. The locus of the calculated critical concentrations is in a good agreement with the experimental phase diagram of the solutions. The proposed mechanism of the metal-nonmetal transition is quite general and may occur in systems involving self-trapped quantum quasiparticles. |
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