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Exact-two-component block-localized wave function: A simple scheme for the automatic computation of relativistic
Adam Grofe1, Jiali Gao2, Xiaosong Li1
1Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
The Journal of Chemical Physics
|July 9, 2021
Summary
We extended the block-localized wave function method to relativistic two-component systems. This approach helps optimize excited states but can break symmetries like total angular momentum, especially with density functional theory.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Relativistic Quantum Mechanics
Background:
- The block-localized wave function (BLW) method is crucial for optimizing constrained determinants in electronic structure calculations.
- Relativistic effects become significant for heavy elements, necessitating specialized computational frameworks.
Purpose of the Study:
- To extend the generalized block-localized wave function (GBLW) technique to a relativistic two-component framework.
- To investigate the optimization of excited state determinants within this relativistic context.
- To analyze the preservation of symmetries (time-reversal and total angular momentum) during ΔSCF optimization.
Main Methods:
- Implementation of the GBLW method within a relativistic two-component framework.
- Application of ΔSCF (Δ self-consistent field) optimization for excited states.
- Testing on a series of atomic systems to evaluate symmetry preservation.
Main Results:
- Time-reversal symmetry is generally maintained with Hartree-Fock but less so with Kohn-Sham density functional theory.
- Total angular momentum symmetry preservation is system-dependent and not guaranteed.
- Breaking of total angular momentum symmetry was traced to the relaxation of core electrons.
Conclusions:
- The relativistic GBLW method is a viable approach for optimizing excited state determinants.
- Symmetry breaking, particularly of total angular momentum, is a key consideration in relativistic excited state calculations.
- Further investigation is needed to fully understand and control symmetry in these relativistic calculations.
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