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Positron affinities of polyatomic molecules: implementation of explicitly correlated Gaussians in the any particle molecular orbital method

Abstract

This Research Proposal aims at evaluating positron affinities of polyatomic molecules (positron-molecule binding energies). Prof. Andrés Reyes (National University of Colombia, Visiting Researcher) developed in collaboration with Prof. Roberto Flores Moreno (Universdade of Guadalajara), the methodology Any Particle Molecular Orbital (APMO), which allows for studies of systems comprising more than one species of quantum particles. The APMO method has been applied to systems containing quantum electrons and quantum nuclei [Romero et al., J. Chem. Phys. 137, 074105 (2012)] and will be extended to systems with quantum electrons and quantum positrons. During the visit, the use of Explicitly Correlated Gaussians (ECGs) will be implemented in the APMO code. The use of correlated atomic orbitals is very important to describe the dynamical correlation and will follow the numerically efficient strategy recently proposed by Nakai and co-workers for the quantum electron-nuclear problem [Hoshino et al., J. Chem. Phys. 135, 024111 (2011)]. The group of Prof. Márcio Varella at São Paulo University (Host Researcher) has developed models for resonant positron annihilation on molecules [Sanchez et al., Phys. Rev. A 90, 052710 (2009)]. These models employ empirical parameters related to positron-molecule binding energies as well as to vibrational couplings. The implementation of the ECG-APMO methodology will allow for ab inito estimates of the model parameters used in annihilation theories [Sanchez et al., Phys. Rev. Lett. 107, 103201 (2011)]; these parameters have so far been treated empirically. As a consequence, the visit of Prof. Reyes to São Paulo University (USP) will cement a collaboration with great potential of impacting the field of positron-molecule interactions, one of the main research lines of the USP group. The Host Researcher is also involved in studies of positron scattring from molecules employing the Schwinger Multichannel method (SMC) [Germano and Lima, Phys. Rev. A 47, 3976 (1993)], in collaboration with other institutions in Brazil (UFPR, UNICAMP) and elsewhere (Trento University, Italy and Flinders University, Australia). During the visit, the USP group will also discuss with Prof. Reyes some strategies to improve the SMC algorithm, such as the implementation of ECGs. Finally, Prof. Reyes (Full Professor of Chemistry in the National University of Colombia) will also teach short courses on Electronic Propapagator Methods and on Multicomponent Methods in Elecetronic Structure during his visit to USP. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
ROMERO, JONATHAN; CHARRY, JORGE A.; FLORES-MORENO, ROBERTO; VARELLA, MARCIO T. DO N.; REYES, ANDRES. Calculation of positron binding energies using the generalized any particle propagator theory. Journal of Chemical Physics, v. 141, n. 11 SEP 21 2014. Web of Science Citations: 15.
CHARRY, J.; ROMERO, J.; VARELLA, M. T. DO N.; REYES, A. Calculation of positron binding energies of amino acids with the any-particle molecular-orbital approach. Physical Review A, v. 89, n. 5 MAY 14 2014. Web of Science Citations: 16.

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