Spin-crossover complexes: Self-interaction correction vs density correction.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Transition metal complexes with 3d4-3d7 electron configurations exhibit high-spin (HS) and low-spin (LS) states.
• The spin-crossover energy, the difference between HS and LS states, is small and difficult to calculate accurately.
• Accurate calculation of spin-crossover energies is crucial for understanding and designing materials with tunable magnetic properties.

Purpose of the Study:

• To evaluate the accuracy of various electronic structure approximations for calculating spin-crossover energies.
• To investigate the impact of self-interaction correction on the accuracy of spin-crossover energy calculations.
• To identify methods that can reliably predict spin-crossover energies in iron complexes.

Main Methods:

• Calculations of spin-crossover energies for iron complexes using methods based on the random phase approximation (RPA) and Fermi-Löwdin self-interaction correction (FL-SIC).
• Comparison of self-consistent and post-self-consistent calculation results.
• Analysis of Hartree-Fock (HF) densities and their resemblance to Perdew-Zunger-type self-interaction corrected (PZ-SIC) densities.

Main Results:

• Evaluating exchange-correlation energy functionals on self-interaction-corrected densities mitigates density errors.
• This approach improves the accuracy of adiabatic energy differences between high-spin and low-spin states.
• The study highlights the importance of density accuracy for reliable spin-crossover energy predictions.

Conclusions:

• Self-interaction corrected densities offer a promising route to improve the accuracy of spin-crossover energy calculations.
• The findings provide guidance for selecting appropriate electronic structure methods for studying spin-crossover phenomena.
• Accurate theoretical predictions of spin-crossover energies are essential for advancing molecular magnetism and materials science.