Tensor-decomposed vibrational coupled-cluster theory: Enabling large-scale, highly accurate vibrational-structure...

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Molecular Spectroscopy

Background:

• Vibrational coupled-cluster (VCC) theory provides accurate molecular vibrational energies.
• Conventional VCC methods face significant computational scaling and memory challenges for larger systems.
• The canonical polyadic (CP) format offers a potential solution for these limitations.

Purpose of the Study:

• To present a new implementation of VCC theory using the CP format.
• To develop and discuss the general algorithm for evaluating VCC error vectors in CP format.
• To assess the computational scaling and memory efficiency of the CP-VCC algorithm.

Main Methods:

• Implementation of vibrational coupled-cluster (VCC) theory utilizing the canonical polyadic (CP) format for all amplitude tensors.
• Development of an algorithm to solve non-linear VCC equations without full-dimension amplitude or error vector construction.
• Application of rank-reduction methods during the summation of terms in VCC amplitude equations.
• Benchmark calculations on molecules like thiadiazole and polycyclic aromatic hydrocarbons to evaluate performance.

Main Results:

• The CP-VCC algorithm achieves the same vibrational energies as conventional VCC methods.
• Demonstrated significant reductions in computational scaling and memory requirements compared to traditional approaches.
• Enabled high-order VCC calculations for systems with up to 66 vibrational modes, such as anthracene.
• Successfully performed calculations on systems that are intractable with conventional VCC methods.

Conclusions:

• The CP-VCC algorithm offers a computationally efficient alternative for high-accuracy VCC calculations.
• This method significantly expands the scope of VCC theory to larger and more complex molecular systems.
• The CP-VCC approach paves the way for accurate vibrational spectra and property predictions in larger molecules.