On the thermodynamics of phase transitions in metal hydrides

• Authors: Andrea Vita
• Languages of publication: EN

Abstracts

EN

Metal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier’s principle of thermodynamics to a particular phase transition in TiHx, which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H+ ions and of the distance between adjacent H+ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H+ ions (‘collective modes’) increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H+ ions with collective modes makes a tiny suprathermal fraction of the H+ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.

Keywords

EN

metal hydrides; phase transitions; thermodynamics; statistical mechanics

• Publisher: De Gruyter Open
• Journal: Open Physics
• Year: 2012
• Volume: 10
• Issue: 1
• Pages: 86-95

Dates

published

1 - 2 - 2012

online

3 - 12 - 2011

Contributors

author

Andrea Vita

• DICAT, Universita’ di Genova-1, via Montallegro, 16145, Genova, Italy

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Identifiers

DOI

10.2478/s11534-011-0094-4