Scalable Electron Correlation Methods. 5. Parallel Perturbative Triples Correction for Explicitly Correlated Local...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Coupled cluster methods are essential for accurate electronic structure calculations.
• Pair natural orbital (PNO) based methods reduce computational cost by localizing electron correlation.
• Perturbative triples corrections are crucial for high accuracy but computationally expensive.

Purpose of the Study:

• To develop and implement a well-parallelized perturbative triples correction for PNO-based coupled cluster (PNO-LCCSD(T)-F12).
• To improve the efficiency and scalability of high-accuracy coupled cluster calculations for large molecular systems.

Main Methods:

• A composite approach combining local triples amplitudes in small domains with semicanonical domain corrections in larger domains.
• A two-step triple list selection strategy to minimize computational effort.
• Implementation of a well-parallelized algorithm for efficient computation on modern hardware.

Main Results:

• The new method adds only ~20% to the computational cost of the triples correction.
• Relative energy calculations show agreement within ~0.5 kcal mol⁻¹ with canonical methods.
• The cost scales linearly with system size and exhibits excellent parallelization efficiency.
• Accurate results for systems with ~100 atoms are achievable in hours on a commodity cluster.

Conclusions:

• The developed PNO-LCCSD(T)-F12 method provides a computationally efficient and accurate way to include triples corrections.
• The findings enable high-accuracy electronic structure calculations for previously intractable large molecular systems.
• The study highlights the need for refined triple selection criteria in local triples methods for large systems.