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Updated: Jul 31, 2025
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Generation and Coherent Control of Pulsed Quantum Frequency Combs
Published on: June 8, 2018
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Toward Compact Selected Configuration Interaction Wave Functions with Quantum Monte Carlo─A Case Study of C2
Jil Ludovicy1, Robin Dahl1, Arne Lüchow1
1Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany.
Journal of Chemical Theory and Computation
|May 2, 2023
Summary
This study enhances quantum Monte Carlo methods for investigating the C2 molecule's ground state. Optimized wave functions yield accurate energies, improving computational chemistry predictions.
Area of Science:
- Quantum chemistry
- Computational physics
- Molecular spectroscopy
Background:
- The accurate description of molecular electronic structure is crucial for understanding chemical bonding and reactivity.
- Quantum Monte Carlo (QMC) methods offer a powerful approach for solving the Schrödinger equation, but their efficiency depends on the quality of the wave function.
- Configuration Interaction (CI) methods can systematically improve wave functions but become computationally expensive with increasing system size.
Purpose of the Study:
- To investigate the ground state of the C2 molecule using advanced quantum Monte Carlo techniques.
- To develop and assess truncated Configuration Interaction with a Jastrow (CIPSI-Jastrow) wave function ansatz.
- To optimize wave function parameters for improved accuracy in energy calculations.
Main Methods:
- Utilized variational and diffusion quantum Monte Carlo (VMC and DMC) methods.
- Employed truncated CIPSI-Jastrow Configuration State Function (CSF) wave functions with Hartree-Fock orbitals.
- Performed partial or full reoptimization of Jastrow, molecular orbital, and CI parameters.
Main Results:
- Achieved excellent absolute and bond dissociation energies for the C2 molecule at the DMC level.
- Demonstrated that compact, fully optimized wave functions lead to high accuracy.
- Observed a significant change in the CI picture upon reoptimization of the antisymmetric part of the wave function.
- Showed that selecting CSFs in the presence of a Jastrow correlation function improves VMC energy and nodal surface quality.
Conclusions:
- The developed truncated CIPSI-Jastrow approach provides a computationally efficient and accurate method for electronic structure calculations.
- Reoptimization strategies are key to improving the quality of wave functions in QMC.
- This work lays the foundation for a novel Jastrow-selected CI scheme within quantum Monte Carlo frameworks.
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