Four-component relativistic time-dependent density-functional theory using a stable noncollinear DFT ansatz...

Area of Science:

• Theoretical Chemistry
• Quantum Chemistry
• Computational Physics

Background:

• Relativistic effects are crucial for accurate electronic structure calculations of heavy elements.
• Time-dependent density functional theory (TD-DFT) is a powerful tool for studying electronic excitations.
• Previous relativistic TD-DFT methods faced limitations with open-shell systems and vanishing spin densities.

Purpose of the Study:

• To develop a robust formulation of relativistic linear response TD-DFT.
• To extend the applicability to both closed- and open-shell reference states.
• To improve the treatment of challenging limit cases in electronic structure calculations.

Main Methods:

• Employs a four-component Dirac-Coulomb Hamiltonian framework.
• Utilizes a noncollinear ansatz for improved accuracy.
• Incorporates a Davidson-Olsen solver considering left and right eigenvectors for robust convergence.

Main Results:

• Successfully calculates electronic excitation energies for both closed- and open-shell systems.
• Demonstrates applicability to Group 3 and Group 11 elements.
• Validates the method on actinide complexes with effective doublet ground states.

Conclusions:

• The presented relativistic TD-DFT formulation offers a versatile and accurate approach for electronic excitation energy calculations.
• The method overcomes limitations of previous treatments, particularly for open-shell systems.
• It provides a reliable tool for investigating the electronic properties of heavy elements and compounds.