Convergence Behavior of SymmetryAdapted Perturbation Expansions for Excited States. A Model Study of Interactions Involving a Triplet Helium Atom
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Title:  Convergence Behavior of SymmetryAdapted Perturbation Expansions for Excited States. A Model Study of Interactions Involving a Triplet Helium Atom 

Creators:  Przybytek, Michał Patkowski, Konrad Jeziorski, Bogumił 

Journal or Publication Title:  Collection of Czechoslovak Chemical Communications, 69, 1, pp. 141176 

Uncontrolled Keywords:  FCI calculations, Schrödinger equation, Hamiltonian, AmosMusher theory, Weak interactions, Quantum chemistry 

AbstractThe convergence behavior of symmetryadapted perturbation theory (SAPT) expansions is investigated for an interacting system involving an excited, openshell monomer. By performing largeorder numerical calculations for the interaction of the lowest, 1s2s, triplet state of helium with the ground state of the hydrogen atom we show that the conventional polarization and symmetrized RayleighSchrödinger expansions diverge in this case. This divergence is attributed to the continuum of intruder states appearing when the hydrogen electron is falling on the helium 1s orbital and the 2s electron is ejected from the interacting system. One of the dimer states resulting from the interaction becomes then a resonance, which presents a hard case to treat by a perturbation theory. We show that the SAPT expansions employing the strong symmetryforcing procedure, such as the EisenschitzLondon Hirschfeldervan der Avoird or the AmosMusher theories, can cope with this situation and lead to convergent series when the permutational symmetry of the bound, quartet state is forced. However, these theories suffer from a wrong asymptotic behavior of the second and higherorder energies when the interatomic distance <i>R</i> grows to infinity, which makes them unsuitable for practical applications. We show that by a suitable regularization of the Coulomb potential and by treating differently the regular, longrange and the singular, shortrange parts of the interatomic electronnucleus attraction terms in the Hamiltonian one obtains a perturbation expansion which has the correct asymptotic behavior in each order and which converges fast for a wide range of interatomic distances. <p> Title:  Convergence Behavior of SymmetryAdapted Perturbation Expansions for Excited States. A Model Study of Interactions Involving a Triplet Helium Atom 

Creators:  Przybytek, Michał Patkowski, Konrad Jeziorski, Bogumił 

Uncontrolled Keywords:  FCI calculations, Schrödinger equation, Hamiltonian, AmosMusher theory, Weak interactions, Quantum chemistry 

Divisions:  Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications 

Journal or Publication Title:  Collection of Czechoslovak Chemical Communications 

Volume:  69 

Number:  1 

Page Range:  pp. 141176 

ISSN:  00100765 

EISSN:  12126950 

Publisher:  Institute of Organic Chemistry and Biochemistry 

Related URLs:  

ID Code:  2201 

Item Type:  Article 

Deposited On:  06 Feb 2009 17:16 

Last Modified:  06 Feb 2009 16:16 

CitationPrzybytek, Michał; Patkowski, Konrad; Jeziorski, Bogumił (2004) Convergence Behavior of SymmetryAdapted Perturbation Expansions for Excited States. A Model Study of Interactions Involving a Triplet Helium Atom. Collection of Czechoslovak Chemical Communications, 69 (1). pp. 141176. ISSN 00100765Repository Staff Only: item control page
