Modeling positrons in molecular electronic structure calculations with the nuclear-electronic orbital method

Paul E. Adamson, Xiaofeng F. Duan, Larry W. Burggraf, Michael V. Pak, Chet Swalina, Sharon Hammes-Schiffer

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34 Scopus citations


The nuclear-electronic orbital (NEO) method was modified and extended to positron systems for studying mixed positronic-electronic wavefunctions, replacing the mass of the proton with the mass of the positron. Within the modified NEO framework, the NEO-HF (Hartree-Fock) method provides the energy corresponding to the single-configuration mixed positronic-electronic wavefunction, minimized with respect to the molecular orbitais expressed as linear combinations of Gaussian basis functions. The electron-electron and electron-positron correlation can be treated in the NEO framework with second-order perturbation theory (NEO-MP2) or multiconfigurational methods such as the full configuration interaction (NEO-FCI) and complete active space self-consistent-field (NEO-CASSCF) methods. In addition to implementing these methods for positronic systems, strategies for calculating electron-positron annihilation rates using NEO-HF, NEO-MP2, and NEO-FCI wavefunctions were also developed. To apply the NEO method to the positronium hydride (PsH) system, positronic and electronic basis sets were optimized at the NEO-FCI level and used to compute NEO-MP2 and NEO-FCI energies and annihilation rates. The effects of basis set size on NEO-MP2 and NEO-FCI correlation energies and annihilation rates were compared. Even-tempered electronic and positronic basis sets were also optimized for the e+LiH molecule at the NEO-MP2 level and used to compute the equilibrium bond length and vibrational energy.

Original languageEnglish (US)
Pages (from-to)1346-1351
Number of pages6
JournalJournal of Physical Chemistry A
Issue number6
StatePublished - Feb 14 2008
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry


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