Beyond CCSD(T) Accuracy at Lower Scaling with Auxiliary Field Quantum Monte Carlo

Area of Science:

• Quantum chemistry
• Computational physics
• Materials science

Background:

• Accurate electronic structure calculations are crucial for understanding molecular properties and chemical reactions.
• Coupled cluster singles and doubles with perturbative triples (CCSD(T)) is a widely used benchmark method, but computationally expensive.
• Configuration interaction singles and doubles (CISD) offers a simpler approximation but often lacks sufficient accuracy.

Purpose of the Study:

• To introduce a novel black-box auxiliary field quantum Monte Carlo (AFQMC) method.
• To achieve highly accurate electronic structure calculations using CISD trial states.
• To compare the accuracy and computational cost against the CCSD(T) benchmark.

Main Methods:

• Development of a black-box auxiliary field quantum Monte Carlo (AFQMC) approach.
• Utilizing configuration interaction singles and doubles (CISD) as trial wave functions.
• Performing calculations on challenging main group and transition metal-containing molecules.

Main Results:

• The AFQMC method consistently yields more accurate energy estimates than CCSD(T).
• The computational cost scales as O(N^6), which is more favorable than CCSD(T)'s O(N^7) scaling.
• Demonstrated accuracy on complex molecular systems, including those with transition metals.

Conclusions:

• The proposed AFQMC method offers a more accurate and computationally efficient alternative to CCSD(T) for electronic structure calculations.
• This advancement has significant implications for theoretical chemistry and materials science, enabling the study of larger and more complex systems.
• The method's black-box nature and improved scaling make high-accuracy quantum chemistry more accessible.