Relativistic Coupled Cluster with Completely Renormalized and Perturbative Triples Corrections

Area of Science:

• Quantum Chemistry
• Relativistic Calculations
• Computational Spectroscopy

Background:

• Coupled-cluster with single and double excitations (CCSD) is a standard method for electronic structure calculations.
• Relativistic effects become significant for heavy elements like gold and silver.
• Accurate potential energy curves and spectroscopic constants are vital for understanding molecular properties.

Purpose of the Study:

• To implement and assess noniterative triples corrections within the 1-electron exact two-component (1eX2C) relativistic framework for CCSD.
• To investigate the impact of relativistic effects and electron correlation on the properties of copper, silver, and gold dimers.
• To evaluate the performance of CCSD(T) and completely renormalized (CR) CC(2,3) methods for these systems.

Main Methods:

• Implementation of noniterative triples corrections to CCSD energy.
• Utilizing the 1-electron exact two-component (1eX2C) relativistic framework.
• Performing all-electron computations for potential energy curves and spectroscopic constants.

Main Results:

• Spin-orbit coupling effects are essential for accurate potential energy curves.
• Triples corrections alter dissociation energies by 4-7% (0.1-0.2 eV).
• Relativistic effects and basis set choices are more critical for Au2 than Ag2 or Cu2.

Conclusions:

• The developed methods accurately describe the electronic structure of heavy metal dimers.
• Relativistic effects and electron correlation significantly influence the properties of Ag2 and Au2.
• The study highlights the importance of advanced computational methods for heavy element chemistry.