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Relativistic two-component double ionization potential equation-of-motion coupled cluster with the
Run R Li1, Stephen H Yuwono1, Marcus D Liebenthal1
1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA.
We developed a relativistic computational method to accurately calculate double ionization potentials (DIPs) for atoms and molecules. Our approach shows excellent agreement with other advanced methods and experimental data, improving our understanding of electronic structure.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Relativistic Quantum Mechanics
Background:
- Accurate calculation of electronic properties is crucial for understanding chemical phenomena.
- Relativistic effects become significant for heavy elements and high-precision calculations.
- Double ionization potentials (DIPs) provide insights into the stability and electronic structure of dication species.
Purpose of the Study:
- To implement and apply a relativistic double ionization potential (DIP) equation-of-motion coupled cluster (EOMCC) method.
- To utilize the molecular mean-field exact two-component (mmfX2C) framework for relativistic calculations.
- To investigate the accuracy of the mmfX2C-DIP-EOMCC method by comparing with four-component calculations and experimental data.
Main Methods:
- Implementation of relativistic DIP-EOMCC with up to 4-hole-2-particle (4h2p) excitations.
- Utilizing the molecular mean-field exact two-component (mmfX2C) framework.
- Comparison with four-component DIP-EOMCC calculations using Dirac-Coulomb and Dirac-Coulomb-Gaunt Hamiltonians.
- Comparison with experimental DIPs using the Dirac-Coulomb-Breit Hamiltonian.
Main Results:
- Excellent agreement (within 0.001 eV) between mmfX2C- and four-component DIP-EOMCC (3-hole-1-particle) calculations.
- mmfX2C-DIP-EOMCC with 3-hole-1-particle excitations generally overestimates experimental DIPs for noble gases by 0.1-0.4 eV.
- Inclusion of 4-hole-2-particle excitations leads to calculated DIPs that are too low by 0.1-0.2 eV at the large basis set limit.
Conclusions:
- The mmfX2C-DIP-EOMCC method provides a computationally efficient and accurate approach for calculating relativistic DIPs.
- The level of excitation (3-hole-1-particle vs. 4-hole-2-particle) significantly impacts the accuracy of calculated DIPs.
- Further refinement of excitation levels is necessary for achieving quantitative agreement with experimental data for all systems.
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