A new accurate and full dimensional potential energy surface of H5+ based on a triatomics-in-molecules analytic functional form

Abstract

15 pags. ; 11 figs. ; 2 Appendix ; 4 tabs.In this work a reliable full nine-dimensional potential energy surface for studying the dynamics of H5+ is constructed, which is completely symmetric under any permutation of the nuclei. For this purpose, we develop a triatoms-in-molecules method as an extension of the more common diatoms-in-molecules one, which allows a very accurate description of the asymptotic regions by including correctly the charge-induced dipole and quadrupole interactions. Moreover, this treatment provides a semiquantitative description of all the topological features of the global potential compared with coupled cluster results. In particular, the hop of the proton between two H2 fragments produces a double well in the potential. This resonant structure involving the five atoms produces a stabilization, lowering the barrier, and the triatoms-in-molecules yields to a barrier significantly higher than the ab initio results. Therefore, to improve the triatomics-in-molecules potential surface, two five-body terms are added, which are fitted to more than 110 000 coupled-cluster ab initio points. The global potential energy surface thus obtained in this work has an overall root mean square error of 0.079 kcal/mol for energies below 27 kcal/mol above the global well. The features of the potential are described and compared with previous available surfaces.We acknowledge Professor J. Bowman for providing us the program of their potential energy surface. This work has been supported by Ministerio de Ciencia e Innovación under Grant Nos. CTQ2007-62898, CTQ2007-63332, and FIS2007-62006 and by Comunidad Autónoma de Madrid under Grant No. S-2009/MAT-1467. It has also been founded by the program CONSOLIDER-INGENIO 2010 of Ministerio de Ciencia e Innovación under Grant No. CSD2009-00038 entitled “Molecular Astrophysics: The Herschel and Alma Era.” The calculations have been performed at CESGA and IFF computing centers.Peer reviewe