A Massively Parallel Implementation of the CCSD(T) Method Using the Resolution-of-the-Identity Approximation and a...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• High-Performance Computing

Background:

• Coupled-cluster singles and doubles with perturbative triples [CCSD(T)] is a high-accuracy quantum chemistry method.
• Large-scale CCSD(T) calculations are computationally demanding due to significant memory and CPU requirements.
• The resolution-of-the-identity (RI) approximation is crucial for reducing the computational cost of calculating two-electron repulsion integrals (ERIs).

Purpose of the Study:

• To develop and implement a parallel algorithm for the RI-approximated CCSD(T) method.
• To optimize parallel efficiency for both the CCSD amplitude equations and the computationally intensive triples correction.
• To enable accurate electronic structure calculations for larger and more complex molecular systems.

Main Methods:

• An integral-direct strategy is employed to bypass the storage of four-center ERIs.
• A hybrid MPI/OpenMP parallelization scheme is utilized for efficient intranode and internode communication.
• Two algorithms are implemented for rate-limiting terms, differing in memory usage and scaling behavior.
• Near-linear scaling is achieved for the CCSD(T) calculation on up to 8000 cores.

Main Results:

• The developed parallel algorithm demonstrates near-linear scaling, particularly for the triples correction step.
• Two distinct algorithms for rate-limiting terms show trade-offs between speed and memory efficiency at different core counts.
• Successful application to molecules with up to 51 atoms and 1624 basis functions.
• Accurate calculation of the complete basis set (CBS) limit for the interaction energy of the uracil dimer.

Conclusions:

• The implemented parallel RI-CCSD(T) algorithm significantly enhances computational efficiency for high-accuracy electronic structure calculations.
• The algorithm's scalability allows for routine application to larger molecular systems.
• The accurate interaction energy calculation for the uracil dimer validates the method's performance and applicability.