高圧下における三水素化ナトリウム（NaH₃）の構造と安定性に関する研究
Using diamond anvil cells combined with computational methods, the reaction between NaH and excess H₂ was examined at pressures reaching 78 GPa and temperatures near 2000 K. Powder X-ray diffraction revealed that sodium trihydride (NaH₃) forms above 27 GPa, adopting an orthorhombic crystal structure. Raman spectroscopy demonstrated the presence of quasi-molecular H₂ within the NaH lattice, with the H₂ stretching mode red-shifted by approximately 120 cm⁻¹ at 50 GPa relative to pure hydrogen. NaH₃ remained stable under room-temperature compression up to at least 78 GPa but decomposed below 18 GPa. Contrary to earlier experimental and theoretical predictions, no sodium polyhydrides beyond NaH₃ were produced when NaH was heated in excess H₂ between 27 and 75 GPa.
Quasi-molecular H₂ is incorporated within the NaH lattice, stabilizing an orthorhombic NaH₃ phase under high pressure. Below 18 GPa the structure decomposes, and further hydrogenation to higher polyhydrides does not occur in the 27–75 GPa range.
The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).
See also:
https://h2-papers.org/en/papers/38264124