An integral-factorized implementation of the driven similarity renormalization group second-order multireference...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate prediction of electronic structure is crucial for understanding chemical properties.
• Multireference perturbation theories are essential for systems with strong electron correlation.
• Driven similarity renormalization group (DSRG) methods offer a robust framework for electronic structure calculations.

Purpose of the Study:

• To report an efficient implementation of second-order multireference perturbation theory based on the driven similarity renormalization group (DSRG-MRPT2).
• To reduce the computational cost and memory requirements of DSRG-MRPT2 calculations.
• To benchmark the new implementation on naphthyne isomers and compare with established methods.

Main Methods:

• Implementation of DSRG-MRPT2 utilizing factorized two-electron integrals.
• Exploitation of block structure in reference density matrices to reduce computational cost.
• Benchmarking on ten naphthyne isomers with basis sets up to quintuple-ζ quality.

Main Results:

• The DSRG-MRPT2 implementation achieves computational efficiency comparable to second-order Møller-Plesset perturbation theory.
• Singlet-triplet splittings (ΔST) for naphthyne isomers exhibit significant dependence on equilibrium geometries.
• DSRG-MRPT2 predictions show good agreement with reduced multireference coupled cluster theory results for consistent geometries.

Conclusions:

• The developed DSRG-MRPT2 method provides an efficient and accurate approach for studying electronic structure.
• The strong geometry dependence of ΔST highlights the importance of accurate structural determination in theoretical studies.
• The DSRG-MRPT2 method serves as a valuable tool for investigating complex chemical systems.