Linear-Scaling Local Natural Orbital-Based Full Triples Treatment in Coupled-Cluster Theory

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Coupled-cluster methods are essential for accurate electronic structure calculations.
• Canonical coupled-cluster with singles, doubles, and full triples (CCSDT) is highly accurate but computationally expensive.
• Efficient approximations are needed for large molecular systems.

Purpose of the Study:

• To develop an efficient, linear-scaling implementation of the CCSDT method.
• To enable accurate calculation of electron correlation energy for larger systems.
• To provide a computationally feasible alternative to canonical CCSDT.

Main Methods:

• Domain-based local pair natural orbital (DLPNO) approach applied to CCSDT.
• Utilizing converged DLPNO-CCSD(T) amplitudes as a starting point.
• Employing t1-dressing of integrals and Fock matrices for simplified equations.

Main Results:

• The DLPNO-CCSDT method achieves asymptotically linear scaling.
• Recovered over 99.99% of the canonical CCSDT correlation energy.
• Demonstrated sub-kJ mol⁻¹ errors in relative energies compared to canonical CCSDT.
• Showcased efficiency on large linear alkanes and water clusters.

Conclusions:

• DLPNO-CCSDT offers a computationally efficient and accurate method for high-level electronic structure calculations.
• The method significantly reduces the computational cost of CCSDT.
• This approach opens possibilities for studying larger and more complex molecular systems with high accuracy.