Relativistic state-specific multireference coupled cluster theory description for bond-breaking energy surfaces

Area of Science:

• * Computational chemistry
• * Quantum chemistry
• * Relativistic quantum chemistry

Background:

• * Accurate calculation of molecular properties for heavy elements is challenging.
• * Relativistic effects significantly influence the electronic structure of heavy atoms.
• * Existing methods may struggle with accuracy or computational cost for these systems.

Purpose of the Study:

• * To develop and apply a novel four-component relativistic state-specific multireference coupled cluster (4c-SSMRCC) method.
• * To compute ground-state spectroscopic constants for Ag2, Cu2, Au2, and I2.
• * To investigate the impact of relativistic effects on the electronic structure and bonding of these dimers.

Main Methods:

• * Development of a four-component relativistic state-specific multireference coupled cluster (4c-SSMRCC) approach.
• * Utilization of inexpensive improved virtual orbital-complete active space configuration interaction for reference functions.
• * Application to calculate spectroscopic constants and dissociation energy surfaces.

Main Results:

• * Successful implementation of the 4c-SSMRCC method for heavy element systems.
• * High accuracy in predicting spectroscopic constants for Ag2, Cu2, Au2, and I2, showing good agreement with experimental and theoretical data.
• * Observed relativistic bond stabilization in coinage metal dimers (Ag2, Cu2, Au2).
• * Observed relativistic bond weakening in the I2 dimer.

Conclusions:

• * The 4c-SSMRCC method is a robust and accurate tool for studying electronic structures of heavy element systems.
• * Relativistic effects play a crucial role in determining the bonding characteristics of heavy element molecules.
• * The method's size-extensivity and insensitivity to intruder states make it suitable for dissociation energy calculations.