Converging High-Level Coupled-Cluster Energetics by Monte Carlo Sampling and Moment Expansions

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Accurate determination of electronic energies is crucial in computational chemistry.
• High-level coupled-cluster (CC) calculations provide accurate results but are computationally expensive.
• Truncation in cluster operators can lead to inaccuracies in energy calculations.

Purpose of the Study:

• To develop a new computational approach for determining accurate electronic energies.
• To achieve results equivalent to high-level coupled-cluster (CC) calculations.
• To improve the efficiency of calculating electronic energies with high accuracy.

Main Methods:

• Merging the CC(P;Q) formalism with stochastic configuration interaction and CC ideas.
• Applying the CC(P;Q) formalism to correct energies from truncated cluster operators.
• Utilizing stochastic methods to enhance the efficiency of CC calculations.

Main Results:

• The proposed methodology yields accurate electronic energies comparable to high-level CC calculations.
• Demonstrated ability to recover energetics from CC calculations with full treatment of excited clusters.
• Successful application to molecular examples, validating the approach.

Conclusions:

• The new approach offers a computationally efficient way to obtain accurate electronic energies.
• This method provides a viable alternative to computationally demanding high-level CC calculations.
• The integration of CC(P;Q) and stochastic techniques advances the field of quantum chemistry.