# A simple natural orbital mechanism of "pure" van der Waals interaction in the lowest excited triplet state of the hydrogen molecule.
> 水素分子最低励起三重項状態における純粋ファンデルワールス相互作用の自然軌道機構


## Abstract

This theoretical study examined van der Waals (vdW) interaction in the 3Σu+ state of the hydrogen molecule using density-matrix functional theory. Analysis of the configuration-interaction wave function and the exact natural orbital (NO) expansion revealed that a quantitative description of vdW bonding requires only eight NOs beyond the standard Hartree-Fock determinant. The potential-energy curve near the vdW minimum computed with this compact functional showed excellent agreement with full CI results and the Kolos-Wolniewicz benchmark. Specific products of NOs in the two-electron density were found to generate exchange-correlation holes consistent with the classical picture of dispersion as an instantaneous dipole-induced dipole (and higher multipole) effect, with higher multipoles contributing nearly 50% of the total vdW bond energy. These findings provide a foundation for density-matrix and orbital-dependent functionals applicable to vdW bonding.

### Mechanism

Exchange-correlation holes generated by eight natural orbitals in the CI expansion reproduce the instantaneous dipole-induced dipole dispersion picture; higher multipole contributions account for approximately 50% of the total van der Waals bond energy in the H2 triplet state.

## Bibliographic

- **Authors**: Gritsenko O, Baerends EJ
- **Journal**: J Chem Phys
- **Year**: 2006 (2006-02-07)
- **PMID**: [16468859](https://pubmed.ncbi.nlm.nih.gov/16468859/)
- **DOI**: [10.1063/1.2165183](https://doi.org/10.1063/1.2165183)
- **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 16468859. https://h2-papers.org/en/papers/16468859
> **Source**: PubMed PMID [16468859](https://pubmed.ncbi.nlm.nih.gov/16468859/)