A general implementation of time-dependent vibrational coupled-cluster theory.

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• The time-dependent vibrational coupled cluster (TDVCC) method is a powerful tool for simulating molecular dynamics.
• Previous implementations were limited in their ability to handle general coupling levels.

Purpose of the Study:

• To present the first general excitation level implementation of the TDVCC method.
• To extend the existing framework for time-independent VCC calculations to the time-dependent domain.
• To enable the study of TDVCC[k] hierarchy convergence and develop schemes for higher-order excitations.

Main Methods:

• Extension of the general framework for time-independent VCC to the time-dependent context.
• Development of an efficient TDVCC implementation with general coupling levels in the cluster operator and Hamiltonian.
• Introduction and analysis of three definitions for the TDVCC autocorrelation function (ACF).

Main Results:

• Systematic convergence of the TDVCC[k] hierarchy towards the full-TDVCC limit was demonstrated.
• Accurate quantum-dynamics simulations of large systems, including imidazole, formyl fluoride, and formaldehyde, were performed.
• Intramolecular vibrational-energy redistribution in imidazole was studied via ACF decay, highlighting the importance of product separability.

Conclusions:

• The developed TDVCC implementation is efficient and accurate for quantum dynamics simulations.
• The study provides insights into the convergence properties of the TDVCC hierarchy.
• The findings are crucial for understanding molecular vibrational dynamics and energy redistribution processes.