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

Abstract

<span style="color:black">Spin energetics is one of the biggest challenges associated with energy calculations for electronic structure methods. The energy differences of the spin states in spin-crossover compounds are very small, making them one of the most difficult systems to calculate. Few methods provide accurate results for calculating these energy differences. In addition, studies have usually focused on calculating energetics of single molecules while spin-crossover properties are usually experimentally studied in the solid phase. In this paper, we have used periodic boundary conditions employing methods based on density functional theory to calculate the high- and low-spin energy differences for a test case of twenty extended systems. Compounds with different metals and ligands have been selected, and the results indicate that a semiquantitative description of the energy differences can be obtained with the combination of geometry optimization using the PBE functional including many-body dispersion approach and the use of </span><span style="color:rgb( 55 , 65 , 81 )">meta-GGA</span><span style="color:black"> functionals, as r</span><sup style="color:black">2</sup><span style="color:black">SCAN but especially KTBM24, for the energy calculation. Other hybrid functionals, such as TPSSh, gives generally good results, but the calculation of the exact exchange with periodic boundary conditions involves a huge increase in computer time and computational resources</span><span style="color:rgb( 0 , 0 , 0 )">. It makes the proposed non-hybrid functional approach (KTBM24//PBE+MB) a great advantage for the study of periodic systems.</span>