Ab initio QCISD(T) calculations of the ground potential energy surface of He3+

M. F. Satterwhite, Gregory I. Gellene

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Abstract

The energy of the He3+ ground potential energy surface (PES) has been determined using ab initio techniques at the QCISD(T)/aug-cc-pVTZ level of theory for a sufficient number of geometric configurations of the atoms around the linear symmetric global minimum to allow this region of the PES to be represented by a polynomial function in the normal coordinates complete through sixth order. A value for De = 0.178 ± 0.003 eV is determined, which is slightly larger than those available from previous ab initio studies. The PES exhibits significant anharmonicity, particularly in the pure asymmetric stretching coordinate and in motions involving both the symmetric and asymmetric stretching coordinates which combine to form the dissociation coordinate. A first principles calculation of the ro-vibrational energy levels of He3+ with this PES gives the remarkable result of a zero point energy which is greater than that determined by a harmonic approximation. Difficulties arising from the large anharmonicity of the PES for the theoretical determination of the harmonic asymmetric stretching frequency in past studies are discussed.

Original languageEnglish
Pages (from-to)13397-13401
Number of pages5
JournalJournal of physical chemistry
Volume99
Issue number36
DOIs
StatePublished - 1995

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