# Formation and Stability of Dense Methane-Hydrogen Compounds.
> 高圧下における密度メタン-水素化合物の生成と安定性に関する研究


## Abstract

Using a combination of x-ray diffraction, optical spectroscopy, diamond anvil cell experiments, and density functional theory calculations, the dense CH₄-H₂ system was systematically investigated. At pressures as low as 4.8 GPa, two compounds—CH₄(H₂)₂ and (CH₄)₂H₂—were found to be stable, with the latter showing pronounced stiffening of the intramolecular vibrational mode associated with H₂ units. Upon further compression, a structurally distinct composition, (CH₄)₃(H₂)₂₅, was identified. This compound contains an exceptionally large proportion of molecular hydrogen, becoming the first reported material to exceed 50 wt% H₂. Stabilization of these phases is attributed to nuclear quantum effects, and they remain stable across a wide pressure range extending beyond 160 GPa.

### Mechanism

Nuclear quantum effects stabilize the CH₄-H₂ compounds across a broad pressure range; within (CH₄)₂H₂, extreme hardening of the intramolecular vibrational mode of H₂ units was observed under compression.

## Bibliographic

- **Authors**: Ranieri U, Conway LJ, Donnelly ME, Hu H, Wang M, Dalladay-Simpson P, et al.
- **Journal**: Phys Rev Lett
- **Year**: 2022 (2022-05-27)
- **PMID**: [35687440](https://pubmed.ncbi.nlm.nih.gov/35687440/)
- **DOI**: [10.1103/PhysRevLett.128.215702](https://doi.org/10.1103/PhysRevLett.128.215702)
- **Study type**: other
- **Delivery route**: not specified
- **Effect reported**: not assessed

## Delivery context

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).

## Safety notes

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:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)

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> **Cite as**: H2 Papers — PMID 35687440. https://h2-papers.org/en/papers/35687440
> **Source**: PubMed PMID [35687440](https://pubmed.ncbi.nlm.nih.gov/35687440/)