<i>Ab initio</i> quantum Monte Carlo study of the binding of a positron to alkali-metal hydrides

Kita, Yusuke; Tachikawa, Masanori; Towler, M. D.; Needs, R. J.

doi:10.1063/1.3620151

Cited by 34 publications

(26 citation statements)

References 33 publications

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“…Ps will pileup close to the negative partial charges with the positron facing the molecule. A similar result has already been observed for a positron interacting with alkali-metal hydrides [21].…”

Section: Single-particle Interaction Potentialssupporting

confidence: 86%

Pick-Off Annihilation of Positronium in Matter Using Full Correlation Single Particle Potentials: Solid He

2015

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We investigate the modeling of positronium (Ps) states and their pick-off annihilation trapped at open volumes pockets in condensed molecular matter. Our starting point is the interacting many-body system of Ps and a He atom because it is the smallest entity that can mimic the energy gap between the highest occupied and lowest unoccupied molecular orbitals of molecules and yet the the many-body structure of the HePs system can be calculated accurately enough. The exactdiagonalization solution of the HePs system enables us to construct a pair-wise full-correlation single-particle potential for the Ps-He interaction and the total potential in solids is obtained as a superposition of the pair-wise potentials. We study in detail Ps states and their pick-off annihilation rates in voids inside solid He and analyse experimental results for Ps-induced voids in liquid He obtaining the radii of the voids. More importantly, we generalize our conclusions by testing the validity of the Tao-Eldrup model, widely used to analyse ortho-Ps annihilation measurements for voids in molecular matter, against our theoretical results for the solid He. Moreover, we discuss the influence of the partial charges of polar molecules and the strength of the van der Waals interaction on the pick-off annihilation rate.

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Section: Single-particle Interaction Potentialssupporting

confidence: 86%

Pick-Off Annihilation of Positronium in Matter Using Full Correlation Single Particle Potentials: Solid He

2015

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“…(23). The interspecies contributions involving two-species interactions are denoted by 1 αβ 3 pp (ω α ) and 2 αβ 3 pp (ω α ), and correspond to two different classes of diagrams (see Appendix A for a definition of these terms).…”

Section: Quasiparticle (Diagonal) Apmo Propagator Methodsmentioning

confidence: 99%

“…Explicitly correlated Gaussian (ECG) methodologies, [4][5][6][7][8] quantum Monte Carlo (QMC), [9][10][11] and full configuration interaction (FCI) 12,13 methods have demonstrated superior performance in the description of e-p correlation and the estimation of positron binding energies, PBEs. Despite their proven accuracy, these approaches are extremely computationally demanding and calculations are only feasible for relatively small systems, namely, atoms, [14][15][16][17][18][19] diatomic molecules, 18,[20][21][22][23] and linear triatomics. 14,24 A notable exception is the positron-formaldehyde study by Strasburger.…”

Section: Introductionmentioning

confidence: 99%

Calculation of positron binding energies using the generalized any particle propagator theory

Romero

Charry

Flores‐Moreno

et al. 2014

The Journal of Chemical Physics

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We recently extended the electron propagator theory to any type of quantum species based in the framework of the Any-Particle Molecular Orbital (APMO) approach [J. Romero, E. Posada, R. Flores-Moreno, and A. Reyes, J. Chem. Phys. 137, 074105 (2012)]. The generalized any particle molecular orbital propagator theory (APMO/PT) was implemented in its quasiparticle second order version in the LOWDIN code and was applied to calculate nuclear quantum effects in electron binding energies and proton binding energies in molecular systems [M. Díaz-Tinoco, J. Romero, J. V. Ortiz, A. Reyes, and R. Flores-Moreno, J. Chem. Phys. 138, 194108 (2013)]. In this work, we present the derivation of third order quasiparticle APMO/PT methods and we apply them to calculate positron binding energies (PBEs) of atoms and molecules. We calculated the PBEs of anions and some diatomic molecules using the second order, third order, and renormalized third order quasiparticle APMO/PT approaches and compared our results with those previously calculated employing configuration interaction (CI), explicitly correlated and quantum Montecarlo methodologies. We found that renormalized APMO/PT methods can achieve accuracies of ~0.35 eV for anionic systems, compared to Full-CI results, and provide a quantitative description of positron binding to anionic and highly polar species. Third order APMO/PT approaches display considerable potential to study positron binding to large molecules because of the fifth power scaling with respect to the number of basis sets. In this regard, we present additional PBE calculations of some small polar organic molecules, amino acids and DNA nucleobases. We complement our numerical assessment with formal and numerical analyses of the treatment of electron-positron correlation within the quasiparticle propagator approach.

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“…The many-body wave functions of small positronic systems composed by a positron interacting with a light atom or a small molecule can be calculated to a good accuracy using the quantum Monte Carlo (QMC) [11][12][13][14][15][16] and configurationinteraction (CI) [17] methods. In this work, we have obtained accurate positron energies and densities for positronic atoms including a positron (e + H, e + He, e + Li, and e + Be) and Ps (HPs and LiPs) by an exact diagonalization stochastic variational method (SVM) using an explicitly correlated Gaussian (ECG) function basis set.…”

Section: Introductionmentioning

confidence: 99%

Full-correlation single-particle positron potentials for a positron and positronium interacting with atoms

2014

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In this work we define single-particle potentials for a positron and a positronium atom interacting with light atoms (H, He, Li and Be) by inverting a single-particle Schrödinger equation. For this purpose, we use accurate energies and positron densities obtained from the many-body wavefunction of the corresponding positronic systems. The introduced potentials describe the exact correlations for the calculated systems including the formation of a positronium atom. We show that the scattering lengths and the low-energy s-wave phase shifts from accurate many-body calculations are well accounted for by the introduced potential. We also calculate self-consistent two-component density-functional theory positron potentials and densities for the bound positronic systems within the local density approximation. They are in a very good agreement with the many-body results, provided that the finite-positron-density electron-positron correlation potential is used, and they can also describe systems comprising a positronium atom. We argue that the introduced single-particle positron potentials defined for single molecules are transferable to the condensed phase when the inter-molecular interactions are weak. When this condition is fulfilled, the total positron potential can be constructed in a good approximation as the superposition of the molecular potentials.

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Ab initio quantum Monte Carlo study of the binding of a positron to alkali-metal hydrides

Cited by 34 publications

References 33 publications

Pick-Off Annihilation of Positronium in Matter Using Full Correlation Single Particle Potentials: Solid He

Pick-Off Annihilation of Positronium in Matter Using Full Correlation Single Particle Potentials: Solid He

Calculation of positron binding energies using the generalized any particle propagator theory

Full-correlation single-particle positron potentials for a positron and positronium interacting with atoms

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