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Treating Spin-Orbit Coupling and Spin-Spin Coupling in the Framework of the Iterative Configuration Expansion
Lucas Lang1, Vijay Gopal Chilkuri1, Frank Neese1
1Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.
This study implements spin-dependent operators for the iterative configuration expansion (ICE) selected CI method, enabling accurate calculations of magnetic properties for open-shell molecules.
Area of Science:
- Quantum Chemistry
- Computational Chemistry
- Molecular Spectroscopy
Background:
- Spin-adapted configuration state functions (CSFs) offer a compact basis for open-shell systems.
- The iterative configuration expansion (ICE) selected configuration interaction (CI) method is a recent advancement in electronic structure theory.
Purpose of the Study:
- To implement spin-dependent operators within the ICE selected CI framework.
- To extend the capabilities of ICE-CI to include spin-orbit and spin-spin coupling.
- To enable accurate computation of magnetic properties for open-shell molecules.
Main Methods:
- Implementation of spin-dependent operators (spin-orbit, spin-spin coupling) for quasidegenerate perturbation theory.
- Evaluation of matrix elements of spin tensor excitation operators between CSFs.
- Utilizing nonrelativistic/scalar-relativistic ICE wave functions as a starting point.
Main Results:
- Successful implementation of spin-dependent operators for ICE selected CI.
- Demonstration of the method's capability through applications.
- Accurate calculation of electron paramagnetic resonance g-factors and zero-field splitting.
Conclusions:
- The new implementation extends ICE selected CI to accurately compute magnetic properties.
- The method is suitable for studying open-shell systems with spin-dependent interactions.
- Provides a valuable tool for theoretical spectroscopy and catalysis research.
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