Benchmarking Periodic Density Functional Theory Calculations for Spin-State Energies in Spin-Crossover Systems.

Area of Science:

• Computational chemistry
• Materials science
• Solid-state physics

Background:

• Spin energetics pose significant challenges for electronic structure calculations.
• Accurately computing small energy differences between spin states in spin-crossover (SCO) compounds is difficult.
• Most studies focus on single molecules, not the solid-phase SCO properties relevant to experiments.

Purpose of the Study:

• To develop and validate an efficient computational method for calculating spin-crossover energy differences in extended systems.
• To assess the performance of various density functional theory (DFT) functionals for SCO energetics in periodic systems.
• To identify a computationally feasible approach for studying SCO phenomena in solid materials.

Main Methods:

• Utilized periodic boundary conditions within density functional theory (DFT).
• Employed geometry optimization with the PBE functional and many-body dispersion (MB) correction.
• Calculated high- and low-spin energy differences using meta-GGA functionals (r2SCAN, KTBM24) and hybrid functionals (TPSSh).

Main Results:

• A semiquantitative description of energy differences was achieved for 20 extended systems.
• The combination of PBE+MB for geometry and KTBM24 for energy (KTBM24//PBE+MB) showed excellent performance.
• Hybrid functionals like TPSSh provided good results but were computationally expensive due to exact exchange calculations.

Conclusions:

• The nonhybrid KTBM24//PBE+MB approach offers a computationally advantageous method for studying spin-crossover energetics in periodic systems.
• This method provides a viable alternative to more computationally demanding hybrid functionals.
• The findings facilitate accurate theoretical investigations of SCO materials in the solid phase.