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Semi-classical model and assessment of the two-electron atomic system energy in s orbitals
[Modèle semi-classique et évaluation de l’énergie du système atomique à deux électrons dans les orbitales s]
Comptes Rendus. Physique, Volume 26 (2025), pp. 681-695

For physics and engineering undergraduate students, the semi-classical model formulation is a convenient approach to understanding electron behavior, which in turn facilitates the comprehension of more elaborate quantum mechanical formulations. In this line of thought, a two-electron atom semi-classical model was developed for the ground-state energy and excited states of He and ions. The two electrons are in a state occupying the same s orbital; thus, the average position distance was worked out from the classical orbital radius. Utilizing the Coulombic repulsion force between the electrons and the virial theorem, a relationship is established. Numerical results against optical spectroscopy yield an average energy relative error $< 0.23 \%$. When compared against ab initio calculations, the average energy relative error is $< 2.15 \%$. Exact energy values of the system for helium using ICI, QD Monte Carlo, variational and CCSD methods assessed the model. These latter results comparison can serve the purpose of illustrating to the undergraduate student that semi-classical models, although not entirely accurate, can still provide a close agreement with the scientific fundamentals to comprehend the physics behind electrons’ behavior.

Pour les étudiants de premier cycle en physique et en ingénierie, la formulation du modèle semi-classique est une approche pratique pour comprendre le comportement des électrons, ce qui facilite une compréhension plus approfondie des formulations plus élaborées de la mécanique quantique. Dans cette optique, un modèle semi-classique d’atome à deux électrons a été développé pour l’énergie de l’état fondamental et les états excités de He et des ions. Les deux électrons occupent la même orbitale s ; la distance de position moyenne a donc été calculée à partir du rayon de l’orbite classique. En utilisant la force de répulsion coulombienne entre les électrons et le théorème du viriel, une relation est établie. Les résultats numériques comparés à la spectroscopie optique donnent une erreur énergétique relative moyenne inférieure à 0,23%. Comparés aux calculs ab initio, l’erreur énergétique relative moyenne est inférieure à 2,15%. Les valeurs énergétiques exactes du système pour l’hélium par les méthodes ICI, QD Monte Carlo, variationnelle et CCSD ont permis d’évaluer le modèle. La comparaison de ces derniers résultats peut servir à illustrer à l’étudiant de premier cycle que les modèles semi-classiques, bien que pas tout à fait exacts, peuvent néanmoins fournir un accord étroit avec les fondamentaux scientifiques pour comprendre la physique derrière le comportement des électrons.

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DOI : 10.5802/crphys.267
Keywords: Average distance between two points on a circumference, virial theorem, electron repulsive force, repulsive energy, s orbitals
Mots-clés : Distance moyenne entre deux points sur une circonférence, théorème du viriel, forces de répulsion des électrons, énergie de répulsion, orbitales s

Jorge Andrés Ramos-Grez 1 ; Vicente Bañados-BaySchmith 1 ; Joaquín Meyer-Larraín 2

1 Pontificia Universidad Católica de Chile, School of Engineering, Av. Vicuña Mackenna 4860, Macul, 7820436, Santiago, Chile
2 Pontificia Universidad Católica de Chile, Institute of Physics, Av. Vicuña Mackenna 4860, Macul, 7820436, Santiago, Chile
Licence : CC-BY 4.0
Droits d'auteur : Les auteurs conservent leurs droits
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Jorge Andrés Ramos-Grez; Vicente Bañados-BaySchmith; Joaquín Meyer-Larraín. Semi-classical model and assessment of the two-electron atomic system energy in s orbitals. Comptes Rendus. Physique, Volume 26 (2025), pp. 681-695. doi: 10.5802/crphys.267

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