Home List of Titles Effects of quantum chemistry models for bound electrons on positron annihilation spectra for atoms and small molecules
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- Effects of quantum chemistry models for bound electrons on positron annihilation spectra for atoms and small molecules
- Wang, Feng; Ma, Xiaoguang; Selvam, Lalitha; Gribakin, Gleb; Surko, Clifford M.
- The Doppler-shift spectra of the -rays from positron annihilation in molecules were determined by using the momentum distribution of the annihilation electron-positron pair. The effect of the positron wavefunction on spectra was analysed in a recent paper (Green et al 2012 New J. Phys. 14 035021). In this companion paper, we focus on the dominant contribution to the spectra, which arises from the momenta of the bound electrons. In particular, we use computational quantum chemistry models (Hartree-Fock with two basis sets and density functional theory (DFT)) to calculate the wavefunctions of the bound electrons. Numerical results are presented for noble gases and small molecules such as H 2, N 2, O 2, CH 4 and CF 4. The calculations reveal relatively small effects on the Doppler-shift spectra from the level of inclusion of electron correlation energy in the models. For atoms, the difference in the full-width at half-maximum of the spectra obtained using the Hartree-Fock and DFT models does not exceed 2%. For molecules the difference can be much larger, reaching 8% for some molecular orbitals. These results indicate that the predicted positron annihilation spectra for molecules are generally more sensitive to inclusion of electron correlation energies in the quantum chemistry model than the spectra for atoms are.
- Publication type
- Journal article
- Research centre
- Swinburne University of Technology. Faculty of Life and Social Sciences
- New Journal of Physics, Vol. 14 (Aug 2012), article no. 085022
- Publication year
- FOR Code(s)
- 02 Physical Sciences
- Density-functional theory; Electron and positron scattering; Electron correlation calculations for diatomic molecules; Self-consistent-field methods
- Institute of Physics Publishing
- Publisher URL
- Copyright © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. The published version is reproduced in accordance with the terms of the Creative Commons Attribution-Non-Commercial-ShareAlike 3.0 licence (http://creativecommons.org/licenses/by-nc-sa/3.0/).
- Additional information
- Supported by the Australian Research Council.
- Full text
- Peer reviewed