Improved binding energies for LiPs, e<sup>+</sup>Be, NaPs and e<sup>+</sup>Mg

Mitroy, Jim; Ryzhikh, G. G.

doi:10.1088/0953-4075/34/10/313

Cited by 43 publications

(72 citation statements)

References 40 publications

(71 reference statements)

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“…Such small changes show that the 12s basis is already almost complete. Comparing our 19s binding energy with the stochastic-variational calculation of Mitroy and Ryzhikh [66], which was used as the reference in determining the values of ρ A [43], we see that we have agreement at the level of 0.6%. This very small discrepancy can be ascribed to a slightly different description of the electrostatic field of the Be atom and possibly also due to our basis set not being totally complete.…”

Section: A Atoms: Be Mg He and Armentioning

confidence: 54%

Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis

Swann

Gribakin

2020

Phys. Rev. A

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A model-potential method is employed to calculate binding, elastic scattering, and annihilation of positrons for a number of atoms and small nonpolar molecules, namely, Be, Mg, He, Ar, H 2 , N 2 , Cl 2 , and CH 4 . The model potential contains one free parameter for each type of atom within the target. Its values are chosen to reproduce existing ab initio positron-atom binding energies or scattering phase shifts. The calculations are performed using a Gaussian basis for the positron states, and we show how to obtain values of the scattering phase shifts and normalized annihilation rate Z eff from discrete positive-energy pseudostates. Good agreement between the present results and existing calculations and experimental data, where available, is obtained, including the Z eff value for CH 4 , which is strongly enhanced by a low-lying virtual positron state. An exception is the roomtemperature value of Z eff for Cl 2 , for which the present value is much smaller than the experimental value obtained over 50 years ago. Our calculations predict that among the molecular targets studied, only Cl 2 might support a bound state for the positron, with a binding energy of a few meV.

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Section: A Atoms: Be Mg He and Armentioning

confidence: 54%

Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis

Swann

Gribakin

2020

Phys. Rev. A

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“…They give an electron affinity of 0.0238(4) hartree, a positron affinity (PA) of 0.2294(4) hartree, and a Ps binding energy (BE) of 0.0032(4) hartree. While the electron affinity turns out to be in fair agreement with the experimental value, namely 0.023 hartree [34], both PA and BE are roughly 0.009 hartree smaller than the best estimate [4]. These discrepancies might be due to the absence of polarization effects of the core electrons due to the two active electrons and the positron, and to a relatively inaccurate representation of the 1s 2 electron density by means of a single STO-1s function.…”

Section: The E + Lih Systemmentioning

confidence: 62%

Annihilation rate in positronic systems by quantum Monte Carlo: e+LiH as test case

Mella

Chiesa

Morosi

2002

The Journal of Chemical Physics

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An accurate method to compute the annihilation rate in positronic systems by means of quantum Monte Carlo simulations is tested and compared with previously proposed methods using simple model systems. This method can be applied within all the quantum Monte Carlo techniques, just requiring to accumulate the positron-electron distribution function. The annihilation rate of e + LiH as a function of the internuclear distance is studied using a model potential approach to eliminate the core electrons of Li, and explicitly correlated wave functions to deal with all the remaining particles. These results allow us to compute vibrationally averaged annihilation rates, and to understand the effect of the Li + electric field on positron and electron distributions.

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“…The van der Waals force is therefore an order of magnitude stronger for Ps interacting with Li. Our approximation gives a PsLi bound state with binding energy 0.224 eV, somewhat less than 0.336 eV, the most accurate calculated value [28]. Figure 8 shows our calculated total cross section and its components.…”

Section: Positronium Scattering By Lithium ( Ps(1s)-li(2s))mentioning

confidence: 76%

Positronium–atom collisions

Walters

Sahoo

et al. 2004

Nuclear Instruments and Methods in Physics Research Section B:

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New results are presented for Ps(1s) scattering by H(1s), He(1 1 S) and Li(2s). Calculations have been performed in a coupled state framework, usually employing pseudostates, and allowing for excitation of both the Ps and the atom. In the Ps(1s)-H(1s) calculations the H − formation channel has also been included using a highly accurate H − wave function. Resonances resulting from unstable states in which the positron orbits H − have been calculated and analysed. The new Ps(1s)-He(1 1 S) calculations still fail to resolve existing discrepancies between theory and experiment at very low energies. The possible importance of the Ps − formation channel in all three collision systems is discussed.

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Improved binding energies for LiPs, e⁺Be, NaPs and e⁺Mg

Cited by 43 publications

References 40 publications

Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis

Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis

Annihilation rate in positronic systems by quantum Monte Carlo: e+LiH as test case

Positronium–atom collisions

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Improved binding energies for LiPs, e+Be, NaPs and e+Mg

Cited by 43 publications

References 40 publications

Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis

Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis

Annihilation rate in positronic systems by quantum Monte Carlo: e+LiH as test case

Positronium–atom collisions

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Improved binding energies for LiPs, e⁺Be, NaPs and e⁺Mg