Spin state relaxation of iron complexes: The case for OPBE and S12g

The structures of nine iron complexes that show a diversity of experimentally
observed spin ground states are optimized and analyzed with Density
Functional Theory (DFT). An extensive validation study of the new S12g
functional is performed, with the discussion concerning the influence of the
environment, geometry and its overall performance based on the comparison
with the well proven OPBE functional. The OPBE and S12g functionals give the
correct spin ground state for all investigated iron complexes. Since S12g
performs remarkably well it can be considered a reliable tool for studying
spin state energetics in complicated transition metal systems.