Cholesky Decomposition-Based Implementation of Relativistic Two-Component Coupled-Cluster Methods for Medium-Sized...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Relativistic Quantum Mechanics

Background:

• Coupled-cluster (CC) and equation-of-motion CC (EOM-CC) methods are powerful tools for electronic structure calculations.
• Relativistic effects are crucial for heavy elements like uranium.
• Existing methods can be computationally demanding for medium-sized molecules.

Purpose of the Study:

• To develop and implement a Cholesky decomposition (CD)-based approach for relativistic two-component CC and EOM-CC methods.
• To extend the applicability of these methods to medium-sized molecules.
• To assess the accuracy and efficiency of the new implementation.

Main Methods:

• Implementation of relativistic two-component CC and EOM-CC using an exact two-component Hamiltonian with atomic-mean-field spin-orbit integrals (X2CAMF scheme).
• Utilized atomic-orbital-based algorithms to bypass the need for constructing two-electron integrals and intermediates with high virtual indices.
• Employed Cholesky decomposition for efficient handling of integrals and intermediates.

Main Results:

• The CD-based X2CAMF-CC and EOM-CC methods can correlate approximately 1000 spinors, extending applicability to medium-sized molecules.
• Benchmark calculations on uranium-containing molecules show that a Cholesky threshold of 10^-4 maintains chemical accuracy.
• Demonstrated capability through calculations of the bond-dissociation energy of UF₆ and the excitation energy of a solvated uranyl ion.

Conclusions:

• The CD-based implementation provides an efficient and accurate approach for relativistic CC and EOM-CC calculations.
• This method significantly enhances the capability to study complex systems involving heavy elements.
• The approach is validated for chemical accuracy and shows promise for future applications in computational chemistry.