High-order electron-correlation methods with scalar relativistic and spin-orbit corrections

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Theoretical Chemistry

Background:

• Accurate electronic structure calculations are vital for understanding chemical phenomena.
• Incorporating relativistic effects is essential for heavy elements and high-precision studies.
• Existing ab initio electron-correlation methods often lack comprehensive relativistic treatments.

Purpose of the Study:

• To extend existing ab initio electron-correlation methods with relativistic capabilities.
• To enable parallel execution of these advanced computational programs.
• To accurately model systems where scalar relativistic and spin-orbit effects are significant.

Main Methods:

• Developed computer programs for ab initio electron-correlation methods.
• Integrated scalar relativistic and spin-orbit effective potentials.
• Handled complex-valued, spinless orbitals derived from these potentials.
• Applied high-order coupled-cluster and perturbation theory methods.
• Utilized a composite scheme combining different methods and basis sets for dynamical and non-dynamical correlation.

Main Results:

• Successfully fitted computer-generated programs with relativistic capabilities.
• Extended various high-order electron-correlation methods (coupled-cluster, perturbation theory, configuration-interaction singles, active-space coupled-cluster) to include relativistic effects.
• Demonstrated the utility of a composite scheme for treating dynamical/non-dynamical correlation and relativistic effects.
• Achieved accurate simulations for ionization energies, spectroscopic constants, and photoelectron spectra.

Conclusions:

• The developed computational framework effectively incorporates relativistic effects into ab initio electron-correlation methods.
• The composite scheme provides an efficient and accurate approach for chemical simulations involving spin-orbit effects.
• This work advances the capability for high-accuracy theoretical studies in relativistic quantum chemistry.