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| Home > Publications database > Elastic interaction and phase transition in coherent metal-hydrogen systems |
| Book/Report | FZJ-2017-08317 |
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1974
Kernforschungsanlage Jülich, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/16206
Report No.: Juel-1039-FF
Abstract: We study the statistical mechanics.of hydrogen dissolved in metals. The underlying model is based on the assumption that the dominant attractive interaction between the protons in the metal is of elastic nature. In the f irst part of the paper we review some general properties of the elastic interaction. We then discuss theimportance of boundary conditions for the form of the elastic interaction, which turns out to be of the Curie-Weiss type with macroscopic range. In the second part we investigate the $\alpha - \alpha$' ("gas-liquid") phase transition in the hydrogen lattice fluid. The long-range part of the elastic interaction is treated in mean f ieldapproximation. In the canonical ensemble as opposed to the grand canonical ensemble one f inds no coexisting phases near the critical point. Instead there is a continuous transition which changes into a first-order transition at tricritical points. In the temperature-density region which normally corresponds to the two-phase coexistence region the hydrogen density is inhomogeneous and varies on a macroscopic scale. The peculiar nature of the a-a' phase transition is due to the long-range character of the elastic interaction, which ultimately results from the requirement of coherency of the host crystal. We argue that coherent metal-hydrogen systems off er examples of real systems where the classical theory of phase transitions applies.
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