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Physics-Guided Curve Fitting for Potential-Energy Functions of Diatomic Molecules
  • Karl Irikura
Karl Irikura
National Institute of Standards and Technology
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Abstract

When computing the potential-energy curve of a diatomic molecule for predictive spectroscopy, high-level calculations are usually desired. The best calculations are expensive, so few points are usually available. The points are fitted to a continuous function, such as a polynomial. Ro-vibrational energy levels are then computed using the fitted function, and spectroscopic constants extracted. However, there may be problems with overfitting, with inadequate flexibility of the fitting function, or with dependence of results upon the choice of fitting function. More fundamentally, the fitting function is selected using aesthetics or convenience, instead of physics. Here we suggest using a lower-level, high-resolution ab initio potential as a guide. Instead of fitting the sparse, high-level data directly, the energy differences between the high-level points and the guiding potential are fitted. The results are improved even with an inexpensive guiding potential. This simple strategy involves little additional effort and can be recommended for routine use. It is similar to some interpolation strategies in the literature of polyatomic molecules. When the guiding potential extends beyond the high-level data, extrapolations are also improved.

Peer review status:IN REVISION

20 Apr 2021Submitted to International Journal of Quantum Chemistry
20 Apr 2021Submission Checks Completed
20 Apr 2021Assigned to Editor
22 Apr 2021Reviewer(s) Assigned
22 Apr 2021Review(s) Completed, Editorial Evaluation Pending
22 Apr 2021Editorial Decision: Revise Minor
26 Apr 20211st Revision Received
27 Apr 2021Submission Checks Completed
27 Apr 2021Assigned to Editor
27 Apr 2021Reviewer(s) Assigned
06 May 2021Review(s) Completed, Editorial Evaluation Pending
07 May 2021Editorial Decision: Revise Major