Year: 2026
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Saturated molecules of period 2 p -block atoms, such as CH 4, NH 3, and H 2 O with full octets, are not expected to dimerize by covalent bond formation. A computational examination of NH 3 as an exception is carried out. Quite high in energy relative to the isolated monomers, the covalently bound local singlet hexahydridodinitrogen (N 2 H 6 ) minimum of D 3d symmetry on the potential energy surface of the ammonia pair is probed. The structure and bonding of this double-octet dimer system are confirmed, but we find that the location of the species on the potential energy surface is highly sensitive to model chemistry, especially for post-Hartree–Fock methods. Of several singlet dimer pairs examined herein, no other system with period two p -block central atoms formed stable covalent minima. The prospect for dissociation through competing channels provides strong reasons for pessimism about any realization of the N 2 H 6 species. Yet, the observed energy lowering for N 2 H 6, which is strengthened by Rydberg bonding, challenges chemists to continue pressing against the perceived limits of chemical bonding.
Authors: Kelling J. Donald, George Ruthven
Institution: University of Richmond
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Awards: G1249082144, G8319710975, G832884196
OpenAlex ID: W7150962672