Accurate ab initio determination of the adiabatic potential energy function and the Born-Oppenheimer breakdown corrections for the electronic ground state of LiH isotopologues

Filip Holka, P. Szalay, Julien Fremont, Michael Rey, Kirk A. Peterson, Vladimir G. Tyuterev

Research output: Contribution to journalArticle

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Abstract

High level ab initio potential energy functions have been constructed for LiH in order to predict vibrational levels up to dissociation. After careful tests of the parameters of the calculation, the final adiabatic potential energy function has been composed from: (a) an ab initio nonrelativistic potential obtained at the multireference configuration interaction with singles and doubles level including a size-extensivity correction and quintuple-sextuple extrapolations of the basis, (b) a mass-velocity-Darwin relativistic correction, and (c) a diagonal Born-Oppenheimer (BO) correction. Finally, nonadiabatic effects have also been considered by including a nonadiabatic correction to the kinetic energy operator of the nuclei. This correction is calculated from nonadiabatic matrix elements between the ground and excited electronic states. The calculated vibrational levels have been compared with those obtained from the experimental data [J. A. Coxon and C. S. Dickinson, J. Chem. Phys. 134, 9378 (2004)]. It was found that the calculated BO potential results in vibrational levels which have root mean square (rms) deviations of about 6-7 cm-1 for LiH and ∼3 cm-1 for LiD. With all the above mentioned corrections accounted for, the rms deviation falls down to ∼1 cm -1. These results represent a drastic improvement over previous theoretical predictions of vibrational levels for all isotopologues of LiH.

Original languageEnglish
Article number094306
JournalThe Journal of Chemical Physics
Volume134
Issue number9
DOIs
Publication statusPublished - Mar 7 2011

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Potential energy functions
Ground state
breakdown
potential energy
ground state
Electronic states
electronics
Extrapolation
Kinetic energy
relativistic velocity
deviation
configuration interaction
extrapolation
kinetic energy
dissociation
operators
nuclei
matrices
predictions

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry
  • Medicine(all)

Cite this

Accurate ab initio determination of the adiabatic potential energy function and the Born-Oppenheimer breakdown corrections for the electronic ground state of LiH isotopologues. / Holka, Filip; Szalay, P.; Fremont, Julien; Rey, Michael; Peterson, Kirk A.; Tyuterev, Vladimir G.

In: The Journal of Chemical Physics, Vol. 134, No. 9, 094306, 07.03.2011.

Research output: Contribution to journalArticle

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