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Influence of fourth-order vibrational corrections on semi-experimental (reSE) structures of linear molecules.
- Source :
-
The Journal of chemical physics [J Chem Phys] 2024 Jan 07; Vol. 160 (1). - Publication Year :
- 2024
-
Abstract
- Semi-experimental structures (reSE) are derived from experimental ground state rotational constants combined with theoretical vibrational corrections. They permit a meaningful comparison with equilibrium structures based on high-level ab initio calculations. Typically, the vibrational corrections are evaluated with second-order vibrational perturbation theory (VPT2). The amount of error introduced by this approximation is generally thought to be small; however, it has not been thoroughly quantified. Herein, we assess the accuracy of theoretical vibrational corrections by extending the treatment to fourth order (VPT4) for a series of small linear molecules. Typical corrections to bond distances are on the order of 10-5 Å. Larger corrections, nearly 0.0002 Å, are obtained to the bond lengths of NCCN and CNCN. A borderline case is CCCO, which will likely require variational computations for a satisfactory answer. Treatment of vibrational effects beyond VPT2 will thus be important when one wishes to know bond distances confidently to four decimal places (10-4 Å). Certain molecules with shallow bending potentials, e.g., HOC+, are not amenable to a VPT2 description and are not improved by VPT4.<br /> (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)
Details
- Language :
- English
- ISSN :
- 1089-7690
- Volume :
- 160
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- The Journal of chemical physics
- Publication Type :
- Academic Journal
- Accession number :
- 38174791
- Full Text :
- https://doi.org/10.1063/5.0177694