研究目的
Investigating the numerical stability of time-dependent coupled-cluster theory for many-electron dynamics in intense laser pulses, comparing two coupled-cluster formulations with full configuration interaction theory.
研究成果
The OATDCCD method provides a more stable approximation than TDCCSD theory for the description of laser-driven many-electron dynamics. The enhanced numerical stability of OATDCCD theory is attributed to the use of optimal time-dependent biorthonormal reference determinants. The reference weight is proposed as a diagnostic to identify situations where the TDCCSD and OATDCCD theories become unstable.
研究不足
The study is limited by the computational cost of TDFCI theory, restricting the size of the systems considered in terms of particle number and basis set size. Additionally, the OATDCCD method may become unstable if the reference weight increases beyond 1.
1：Experimental Design and Method Selection:
The study compares the numerical stability of TDCCSD and OATDCCD theories with TDFCI theory for simulating many-electron dynamics in intense laser pulses.
2：Sample Selection and Data Sources:
Simulations are performed for the He and Be atoms, and the LiH molecule using the cc-pVDZ, aug-cc-pVDZ, and cc-pVTZ basis sets.
3：List of Experimental Equipment and Materials:
The PySCF software framework is used for generating Hamiltonian integrals and initial orthonormal orbitals.
4：Experimental Procedures and Operational Workflow:
The electronic system is assumed to be in the ground state at t = 0 a.u. and exposed to a laser pulse polarized along the z-axis. The equations of motion are propagated in time using the Gauss-Legendre integrator.
5：Data Analysis Methods:
The reference weight and the norm of the doubles amplitudes are analyzed to assess the numerical stability of the methods.
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