Time-dependent orbital-optimized coupled-cluster methods families for fermion-mixtures dynamics.

Area of Science:

• Quantum Chemistry
• Computational Physics
• Theoretical Chemistry

Background:

• Coupled-cluster (CC) methods are essential for accurate electronic structure calculations.
• Simulating complex fermionic systems, especially mixtures, presents significant computational challenges.
• Existing methods like time-dependent multiconfiguration self-consistent-field (TDMCSCF) have limitations for certain systems.

Purpose of the Study:

• To develop novel time-dependent coupled-cluster (TDCC) methods for fermion mixtures.
• To provide computationally tractable alternatives to TDMCSCF for systems with arbitrary fermion types and numbers.
• To ensure the developed methods maintain key physical invariances and offer accurate descriptions.

Main Methods:

• Presentation of five time-dependent orbital-optimized coupled-cluster (TDOOCC) methods.
• Derivation of truncation schemes that preserve intragroup orbital rotation invariance.
• Formulation of equations of motion for CC amplitudes and orbitals.
• Four methods are designed to converge to the time-dependent complete active space self-consistent-field (TDCASSCF) limit.

Main Results:

• The proposed TDOOCC methods serve as compact parameterization alternatives to TDMCSCF.
• These methods are applicable to fermion mixtures with arbitrary kinds and numbers of fermions.
• Theoretical analysis demonstrates the applicability of these methods to diverse chemical systems.

Conclusions:

• The developed TDOOCC methods provide a powerful new toolkit for studying interacting fermion systems.
• These methods offer enhanced accuracy and flexibility compared to existing computational approaches.
• The theoretical framework supports broad applications in quantum chemistry and condensed matter physics.