Communication: Evaluating non-empirical double hybrid functionals for spin-state energetics in transition-metal...

Area of Science:

• Computational materials science
• Quantum chemistry
• Solid-state physics

Background:

• Accurate electronic structure calculations are crucial for designing inorganic functional materials.
• Current methods like density functionals and wave function approaches have limitations.
• Double hybrid density functionals show promise for improving material design.

Purpose of the Study:

• To evaluate the performance of double hybrid density functionals for predicting electronic ground states.
• To compare PBE0-DH and PBE-QIDH with existing methods for spin-state splitting energies.
• To investigate the factors contributing to the improved accuracy of double hybrid functionals.

Main Methods:

• Utilizing high-level diffusion Monte Carlo calculations as a reference.
• Assessing PBE0-DH and PBE-QIDH performance against PBE0, B3LYP*, and coupled cluster singles and doubles with perturbative triples (CCSD(T)).
• Examining 16 transition metal (Fe and Co) complexes with varying ligand field strengths.

Main Results:

• PBE0-DH and PBE-QIDH demonstrate significant improvements in computing spin-state splitting energies.
• The inclusion of both Hartree-Fock (HF) exchange and MP2 contributions enhances accuracy.
• Increasing MP2 contributions stabilize low-spin states in transition metal complexes, particularly with high field strength ligands.

Conclusions:

• Double hybrid density functionals offer a superior approach for accurate electronic structure calculations in materials science.
• The balance between HF exchange and MP2 is key to their enhanced performance.
• These findings advance the computational design of inorganic functional materials, especially those involving transition metals.