Families of Superionic Conductors

Selected features of these computational methods, and examples of their application, are described in Chapters 5, 7 and 9. 

In many cases, simulation methods are used in a complementary manner to experimental studies, with the validity of the calculations assessed by comparing simulated properties (e.g., crystal structure and activation energies) with those determined experimentally. The major factor in determining the reliability of all the simulation methods is the accuracy of the description of the interaction between the ions. The majority of studies of ionically conducting systems have utilized parameterized potentials containing explicit expressions for the various interactions (short-range repulsion. Coulomb, etc.), although recent advances in available computer power have enabled the application of ab initio methods (see Chapter 7). 

This section provides an overview of the most important families of compounds which display high values of ionic conductivity. Inevitably, limitations of space mean that a number of interesting systems are not discussed, including several systems which are the subject of current research activity (e.g., the LAM OX compounds [7] and apatite-structured oxides [8]) which do not conveniently fit into one ofthe major groups discussed below. 

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The family of Ag + and Cu + superionic conductors have been extensively studied for many decades, using a wide range of experimental and computational techniques see also Chapter 7. They are principally of interest for fundamental reasons, as model systems in which to characterize the nature ofthe dynamic disorder and to probe the factors which promote high values of ionic conductivity within the solid state. Their commercial applications are generally limited by factors such as chemical stability, the high cost of silver, and their relatively high mass when compared, for example, to lithium-based compounds. 

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