Enabling Accurate and Large-Scale Explicitly Correlated CCSD(T) Computations via a Reduced-Cost and Parallel...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Modeling

Background:

• Explicitly correlated coupled-cluster (CC) and Møller-Plesset perturbation theory (MP2) methods provide high accuracy for molecular electronic structure.
• Scaling limitations of these methods hinder their application to large molecular systems.

Purpose of the Study:

• To develop and benchmark parallel algorithms for accelerating explicitly correlated MP2 and CC calculations.
• To enable accurate computational chemistry for extended molecular systems.

Main Methods:

• A hybrid Open Multi-Processing (OpenMP)/Message Passing Interface (MPI) parallel approach was employed.
• Density fitting formalism and local correlation approximations (frozen natural orbital, natural auxiliary function, natural auxiliary basis) were utilized.
• Explicitly correlated triples correction was incorporated.

Main Results:

• The developed algorithms demonstrate excellent parallel scaling on hundreds of processor cores.
• Highly accurate explicitly correlated CC calculations were achieved for systems previously beyond computational limits (e.g., 60 atoms, 2500 orbitals).
• The approach offers superior accuracy-over-cost performance compared to existing explicitly correlated CC methods.

Conclusions:

• The new parallel algorithms significantly enhance the feasibility of high-accuracy electronic structure calculations for large molecules.
• This work facilitates benchmarking of other methods and advances thermochemistry protocols for larger systems.