| Abstract
| - In a recent paper, we described similarities between the superionic transition in certain crystals and the glasstransition in fragile, supercooled liquids. We now examine the underlying energy landscapes of the fluoridesof lead(II) and calcium, by minimizing the potential energy from configurations along molecular-dynamicstrajectories. The resulting inherent structures are characterized by the number of defects they contain and theinteractions of these defects. We propose a simple explanation for the clustering of these defects, related tothe lattice's strain energy, and discuss its implications for the mechanism of conduction. We also considerthe vibrational densities of states of the inherent structures and test the possibility that an increase in theharmonic vibrational entropy upon defect formation stabilizes the superionic state. A mean-field model withan interaction term varying with the cube-root of the defect concentration describes the inherent structuredefect populations well, and also reproduces the energy and entropy over a significant temperature range.However, a direct examination of the way in which the inherent structure energy depends on the defectconcentration shows that this does not mean that the physical picture used to construct the mean-field freeenergy is correct.
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