A Reduced Cost Two-Component Relativistic Equation-of-Motion Coupled Cluster Method for Ionization Potential

Area of Science:

• Computational chemistry
• Quantum chemistry
• Relativistic quantum chemistry

Background:

• Accurate calculation of ionization potentials (IP) is crucial for understanding molecular electronic structure.
• Relativistic effects become significant for molecules containing heavy elements, necessitating specialized computational methods.
• Existing relativistic IP methods can be computationally demanding.

Purpose of the Study:

• To develop and implement an efficient relativistic IP-EOM-CC method.
• To reduce computational cost while maintaining high accuracy for heavy-element systems.
• To validate the new method against established techniques and experimental data.

Main Methods:

• Implementation of the ionization potential (IP) variant of the equation-of-motion coupled cluster (IP-EOM-CC) method.
• Utilizing the exact two-component atomic mean field (X2CAMF) framework.
• Incorporating Cholesky decomposition (CD) and frozen natural spinors (FNS) approximations for computational efficiency.

Main Results:

• The CD and FNS approximations significantly reduce memory and computational load.
• Calculated IP values closely match those from the four-component relativistic IP-EOM-CC method.
• Benchmark studies show excellent agreement with experimental ionization energies and photoelectron spectra.
• The method was successfully applied to a medium-sized complex, [I(H2O)12]-.

Conclusions:

• The developed relativistic IP-EOM-CC method is computationally efficient and accurate.
• This approach provides a reliable tool for studying ionization potentials of heavy-element molecules.
• The method demonstrates practical applicability for complex chemical systems.