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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Non-Bivariational Time-Dependent Orbital-Quasi-Optimized Coupled-Cluster Methods Family for Fermion-Mixtures Dynamics
Haifeng Lang1, Takeshi Sato1,2,3
1Department of Nuclear Engineering and Management, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan.
Journal of Computational Chemistry
|August 5, 2026
Summary
Researchers developed eighteen new non-bivariational time-dependent orbital-quasi-optimized coupled-cluster (TD-oqoCC-NB) methods. These methods enhance numerical stability for complex systems, offering flexible convergence to the complete active space limit.
Area of Science:
- Quantum Chemistry
- Computational Physics
- Theoretical Chemistry
Background:
- Time-dependent coupled-cluster (CC) methods are crucial for simulating quantum dynamics.
- Previous work established time-dependent orbital-optimized CC (TD-ooCC) methods for stability.
- Extending these methods is necessary for broader applicability in complex systems.
Purpose of the Study:
- To extend TD-ooCC methods to a wider range of non-bivariational approaches.
- To develop eighteen novel time-dependent orbital-quasi-optimized coupled-cluster (TD-oqoCC-NB) methods.
- To investigate their stability, convergence, and applicability to electron and vibrational dynamics.
Main Methods:
- Development of eighteen TD-oqoCC-NB methods by extending TD-ooCC.
- Utilizing constraints in the ansatz to prevent overparameterization and numerical instability.
- Flexible selection of equations of motion for convergence to the complete active space limit.
Main Results:
- Successfully derived eighteen TD-oqoCC-NB methods.
- Demonstrated avoidance of overparameterization and numerical instability.
- Observed violation of the Ehrenfest theorem in all NB methods, even when gauge-invariant.
- Identified novel CC methods for time-independent calculations via stationary conditions.
Conclusions:
- The new TD-oqoCC-NB methods offer enhanced stability and flexible convergence for quantum dynamics.
- These methods provide alternatives to TD-ooCC, with distinct properties regarding the Ehrenfest theorem.
- The research also yields new coupled-cluster methods for static electronic structure problems.
Keywords:
coupled clusterelectronic dynamicsnon‐adiabatic dynamicsorbital optimizationvibrational dynamicsMore Related Videos
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