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Hydrogen divacancy diffusion: a new perspective on H migration in MgH2 materials for energy storage
Estefania German1, Ralph Gebauer2
1Departamento de Física, Universidad Nacional del Sur & IFISUR (UNS-CONICET), Av. Alem 1253, 8000, Bahía Blanca, Argentina. egerman@uns.edu.ar and The Abdus Salam International Center for Theoretical Physics (ICTP), Strada Costiera 11, 34151, Trieste, Italy.
Physical Chemistry Chemical Physics : PCCP
|December 13, 2016
Summary
Hydrogen divacancies in magnesium hydride are favored and diffuse similarly to single vacancies. This research clarifies hydrogen transport in MgH2, crucial for hydrogen storage material applications.
Area of Science:
- Materials Science
- Computational Chemistry
- Solid-State Physics
Background:
- Magnesium hydride (MgH2) is a key material for hydrogen storage.
- Understanding hydrogen transport mechanisms is vital for optimizing MgH2 performance.
- Single hydrogen vacancies have been extensively studied, but divacancy behavior remains less understood.
Purpose of the Study:
- To model the formation and diffusion of hydrogen divacancies in magnesium hydride.
- To compare the energetic favorability and diffusion barriers of divacancies with single vacancies.
- To elucidate the role of divacancies in hydrogen transport kinetics within MgH2.
Main Methods:
- Density Functional Theory (DFT) calculations were employed.
- Modeling focused on the formation energies of divacancies versus isolated vacancies.
- Diffusion barriers for divacancies along different axes were computed and compared to single vacancies.
Main Results:
- Divacancies are energetically more favorable than two isolated hydrogen vacancies in MgH2.
- Calculated diffusion barriers for divacancies are comparable to or lower than those for single vacancies.
- These findings indicate divacancies play a significant role in hydrogen diffusion.
Conclusions:
- Divacancies contribute significantly to hydrogen transport in MgH2.
- The energetic favorability and diffusion characteristics of divacancies impact hydrogen storage kinetics.
- This study provides new insights into the fundamental mechanisms of hydrogen movement in MgH2.
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