Superionic high-temperature

Sprik et al, 1993 Signorini et al, 1990), a typical example being the orientational disorder associated with NH in NH Br. Detailed simulations have been reported on (NaCN),, t(KCN),t and other mixed alkali halides and alkali cyanides. Other systems studied include potassium and calcium nitrate crystals and their mixtures. The transition from the crystalline to the superionic conductor phase in solid electrolytes has also been successfully investigated. Molecular dynamics studies of Agl were carried out by Parrinello, Rahman Vashishta (1983). LijSO has been investigated by molecular dynamics by Impey et al. (1985). Here, the Li ions become mobile at high temperatures. The ions exhibit orientational disorder and the orientational... 

The high-temperature superionic properties of the Ag + and Cu + chalcogenides (of general formula A2X, with A = Ag, Cu and X=S, Se, Te) have been extensively studied. These compounds provide an interesting comparison with their halide counterparts, particularly when probing the effects of the doubled cation density on the ionic diffusion mechanisms and macroscopic ionic conductivity [37]. 

One conventional method of stabilizing the high-temperature superionic phases... 

The possibility of inherent difficulties in the accurate MD simulation of slowly diffusing systems is also to be borne in mind following the finding of discrepancies between experiment and simulation observed in the nonliquid but still very relevant case of the ciystalline superionic conductor CaFj. In this system, Rahman has reported MD diffusivities of F that approach zero, on linear D scale plots of the Fig. 3 type, more rapidly than expected from the observed Arrhenius behavior of the measured diffusivities. (Rahman compared his results with extrapolations of data measured below the weak lambda transition at 1200°C, but the electrical data have validated the extrapolation to the accuracy of the comparison.) Rahman s high-temperature data have been accurately reproduced in one of the authors laboratories using a rather different form of pair potential. ... 

Sum rule for oscillator strengths, 102, 11 If Superconductivity high-temperature, 455 transition temperature, 399 Superionic conductors, 316 Surface dipoles, 399ff, 425ff Surface energy ionic compounds, 336 semiconductors, 230ff simple metals, 401f Surface tension, 233 Surface states... 

In the case of CSHSO4, which exhibits a high temperature superionic phase (cf. Chapter 11 on anhydrous compounds), the above reaction was... 

Alkali hydrogen sulphates and selenates are frequently ferroelectric in their low temperature phases and may exhibit superionic behaviour and a plastic state in their high temperature phases, usually above 400-450 K. 

During the same period, the range and sophistication of the applications developed. Representative new areas included the extensive range of simulation studies of defects in superionic conductors [20] in high-temperature superconductors (see, for example. Refs. [21, 22]) and the detailed studies of the complex defect chemistry arising from the creation of fission products in CUO2 nuclear fuels [23]. 

Dell RM (1975) The application of solid state ionic devices. In Klettz M (ed) Electrode processes in sohd state ionics, NATO advanced study institute series C. Kluwer, Dordrecht, pp 387-410 D nfes G, Madamba MC, Muntasar A (1998) Reactivity and stability of superionics MSnF at high temperature in various media. MRS Proc 547 371-376... 

Solid solutions AgCuX (X = S, Se, Te) at above 473 K go to the superionic phase with a cubic structure [2, 15, 16], This state is characterized by the cation disorder occupying tetrahedral positions in the fee lattice of the chalcogen. The lattice parameters for the high-temperature phase of the compoimds and atomic coordinates are listed in Table 16.1. 

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