Symmetry exploitation in closed-shell coupled-cluster theory with spin-orbit coupling

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Coupled-cluster (CC) methods are essential for accurate electronic structure calculations.
• Incorporating spin-orbit coupling is crucial for molecules with heavy elements.
• Computational cost can be a limiting factor for large molecular systems.

Purpose of the Study:

• To exploit spatial symmetry in coupled-cluster calculations including spin-orbit coupling.
• To improve the efficiency of calculating ground state energy and analytic first derivatives.
• To enable accurate calculations for larger closed-shell molecules with heavy elements.

Main Methods:

• Developed a coupled-cluster (CC) approach incorporating spin-orbit coupling.
• Implemented exploitation of both time-reversal and spatial symmetry (D(2h) and subgroups).
• Utilized symmetry of spin functions and direct product decomposition for computational quantities.

Main Results:

• Demonstrated significant reduction in computational effort beyond the molecular point group order.
• Achieved accurate calculations of ground state energy and analytic first derivatives.
• Successfully applied the method to closed-shell molecules containing heavy elements.

Conclusions:

• Symmetry exploitation is a powerful strategy to enhance the efficiency of CC calculations with spin-orbit coupling.
• This method allows for accurate and feasible computations on larger, heavier molecules.
• The developed approach expands the applicability of high-accuracy quantum chemical methods.