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Description
Solid-state hydrogen storage has become an attractive alternative to conventional hydrogen storage options, such as compressed gas or cryogenic liquid hydrogen, due to its higher operational safety, lower energy demands, and high volumetric hydrogen density. This type of storage is based on the incorporation of hydrogen atoms into the lattice of a host compound, forming metal hydrides.
LaNi$_5$ represents a well-known candidate for solid-state hydrogen storage, providing favourable storage capacity, practical plateau pressure, and ease of activation. Its crystal structure contains multiple interstitial sites available for hydrogen occupation. Using Density Functional Theory (DFT) calculations, we investigated the influence of different hydrogen lattice-site occupations and hydrogen content on the magnetic and electronic properties of LaNi$_5$-based hydrides. Pristine LaNi$_5$ exhibits weak ferrimagnetic behaviour. We found that there is no direct relationship between the total hydrogen content and the resulting magnetic properties. Instead, the magnetic properties are strongly governed by the type of occupied hydrogen site, which is related to the hybridization between Ni $3d$ and H $1s$ states.
The effect of hydrogen incorporation was also investigated in the related LaNiSn system, particularly in the stoichiometric intermetallic LaNiSn compound, for which the available information in the literature remains limited. Bader charge analysis was employed to investigate the redistribution of electron density upon hydrogen incorporation and to provide insight into the changes in the chemical environment of La, Ni, Sn, and H. The obtained results contribute to a better understanding of the relationship between hydrogen-site occupation, electronic structure, and magnetic properties in LaNi$_5$- and LaNiSn-based hydrides.
Computational resources were provided by the e-INFRA CZ project (ID: 90254), supported by the Ministry of Education, Youth and Sports of the Czech Republic. These resources were utilized through IT4Innovations National Supercomputing Center, MetaCentrum as well as CERIT Scientific Cloud. This work was created as part of the project No. CZ.02.01.01/00/22_008/0004631 "Materials and technologies for sustainable development'' within the Jan Amos Komenský Operational Programme, financed by the European Union and from the state budget of the Czech Republic.