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Nanoscience and Nanotechnology
Ab initio calculations; hydrogen; hydrogen storage; magnesium compounds; statistical mechanics; thermodynamics; vacancies (crystal)
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Thermodynamics Of Hydrogen Vacancies In Mgh2 From First-Principles Calculations And Grand-Canonical Statistical Mechanics, R Grau-Crespo, K C. Smith, Timothy Fisher, N H. De Leeuw, U V. Waghmare
Thermodynamics Of Hydrogen Vacancies In Mgh2 From First-Principles Calculations And Grand-Canonical Statistical Mechanics, R Grau-Crespo, K C. Smith, Timothy Fisher, N H. De Leeuw, U V. Waghmare
Birck and NCN Publications
Ab initio calculations and statistical mechanics are combined to elucidate the thermodynamics of H vacancies in MgH2. A general method based on a grand-canonical ensemble of defect configurations is presented to model the exchange of hydrogen between crystalline MgH2 and gas-phase H-2. We find that, even at the lowest hydrogen partial pressures at which the hydride phase is stable, MgH2 is capable of accommodating only very small concentrations of hydrogen vacancies. These vacancies are mainly isolated rather than forming clusters, contrary to what is expected from a simple energetic analysis.