A general code for fitting global potential energy surfaces via CHIPR method: Triatomic molecules

• Published in: Computer physics communications 2020-02, Vol.247, p.106913, Article 106913
• Main Authors: Rocha, C.M.R., Varandas, A.J.C.
• Format: Article
• Language: English
• Subjects: CHIPR; Global potential functions; Potential energy surfaces
• ISSN: 0010-4655; 1879-2944
• DOI: 10.1016/j.cpc.2019.106913

A general program to fit global potential energy surfaces of ABC, AB2, and A3 triatomic molecules to ab initio points is reported. It is based on the Combined-Hyperbolic-Inverse-Power-Representation (CHIPR) method. The final form describes all dissociating fragments, long-range and valence interactions, while warranting the system permutational symmetry. The code yields as output a Fortran 90 subroutine that readily evaluates the potential and gradient at any arbitrary geometry. Program Title: CHIPR-3.0 Program Files doi:http://dx.doi.org/10.17632/8wdv87gt5x.1 Licensing provisions: GPLv3 Programming language: Fortran 90 Supplementary material: Directory “EXAMPLES” contains example files and subroutines. Nature of problem: The version zero of the CHIPR code for up to triatomics, CHIPR-3.0, provides a set of subroutines to fit global potential energy surfaces of any triatomic molecule using ab initio data points. Solution method: CHIPR-3.0 uses the Combined-Hyperbolic-Inverse-Power-Representation (CHIPR) method to interpolate and extrapolate ab initio points. Additional comments including restrictions and unusual features: Besides ab initio data, the program generates a subroutine containing two-body terms whose analytic form is subsequently utilized as program input for the triatomic. The first step is dispensable in case the user supplies his own diatomic curves.