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Møller-Plesset Adiabatic Connection at Large Coupling Strengths for Open-Shell Systems.
Kimberly J Daas1, Eveline Klute1, Michael Seidl1
1Department of Chemistry & Pharmaceutical Sciences and Amsterdam Institute of Molecular and Life Sciences (AIMMS), Faculty of Science, Vrije Universiteit, De Boelelaan 1083, Amsterdam 1081 HV, The Netherlands.
This study extends Møller-Plesset perturbation theory to open-shell systems, revealing a phase diagram for the hydrogen atom and providing estimates for many-electron systems. The research offers new insights into electronic structure calculations.
Area of Science:
- Quantum Chemistry
- Computational Physics
- Electronic Structure Theory
Background:
- The Møller-Plesset perturbation series is a standard weak-coupling expansion in quantum chemistry.
- Previous work focused on closed-shell systems, limiting applicability to open-shell systems, especially at large coupling strengths.
Purpose of the Study:
- To generalize Møller-Plesset perturbation theory to open-shell systems.
- To investigate the adiabatic connection from weak to strong coupling limits.
- To develop accurate methods for calculating electronic structure in open-shell systems.
Main Methods:
- Studying the adiabatic connection, bridging weak and strong coupling regimes.
- Analyzing the hydrogen atom with fractional spins as a model system.
- Developing a large-coupling expansion for open-shell systems.
Main Results:
- An intriguing phase diagram for the hydrogen atom was revealed.
- A closed-form equation for the large-coupling leading order was derived for specific quantum numbers.
- Hydrogen atom results provide variational estimates for general many-electron open-shell systems.
Conclusions:
- The study successfully generalizes Møller-Plesset theory to open-shell systems.
- The derived methods offer accurate variational estimates for electronic structure.
- This work advances the understanding of electron correlation in complex molecular systems.
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