The four-component DFT method for the calculation of the EPR g-tensor using a restricted magnetically balanced basis...

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Four-component relativistic calculations of the electron paramagnetic resonance (EPR) g-tensor traditionally suffer from gauge origin dependence and basis set limitations.
• Previous methods relied on a common gauge origin and restricted kinetically balanced basis sets, leading to unreliable results.

Purpose of the Study:

• To address the gauge dependence in relativistic g-tensor calculations.
• To implement a robust four-component relativistic density functional theory (DFT) method for g-tensor calculations.

Main Methods:

• Incorporation of gauge-including atomic orbitals (GIAOs) for a distributed-origin scheme.
• Utilizing a restricted magnetically balanced (RMB) basis set for the small component of four-component wavefunctions.
• Application of noncollinear Kramers-unrestricted DFT methodology based on the Dirac-Coulomb Hamiltonian.

Main Results:

• The developed method significantly reduces gauge dependence in g-tensor calculations.
• Demonstrated connection between gauge dependence and nonvanishing current density integrals in finite bases.
• Showcased low gauge dependence in cluster calculations and its disappearance in systems with specific point-group symmetries.

Conclusions:

• The implemented four-component relativistic DFT method with GIAOs and RMB basis provides accurate and gauge-independent g-tensor values.
• The findings offer insights into the origins of gauge dependence and strategies for its mitigation in relativistic electronic structure calculations.