Simulation of an excess electron in a hard sphere fluid

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Abstract
A Monte Carlo simulation of an electron in a hard sphere fluid is described. Five thermodynamic states along the isotherm λ=6σ have been examined (λ is the thermal wavelength of the electron, σ is the diameter of a sphere, d=σ/2 is taken as the distance of closest approach between a sphere and the electron). At fluid densities below 0.2σ−3, the electron fluctuates in extended configurations. At higher densities, we find that the fluid of random scatterers localizes the electronic configurations into compact yet fluctuating structures occupying voids in the fluid. Between the densities 0.1 to 0.2σ−3 we observe two relatively stable yet distinct electronic structures, one compact and the other extended. This observation of apparent metastable states seems to imply nonlinearities in the fluctuations of the electron suggestive of phase transition behavior. The statistics of the fluctuations in the compact structures are in perfect agreement with earlier results obtained for an electron in rigid disordered array of scatterers. The results of the simulation for both extended and localized states are compared with those obtained from the integral equation theory of Chandler et al. The Monte Carlo calculations were made possible by the use of the staging algorithm. This renormalization procedure allows for the efficient sampling of electronic and fluid fluctuations that extend over many length scales. The competition between the variety of length scales is intrinsic to the physics of the solvated electron.