Fourth paper from a Short-Term Scientific Mission (STSM) (November 16, 2015)

The collaboration of two research groups: Prof. Marcel Swart (University of Girona) and prof. Maja Gruden (University in Belgrade) started in 2012 and involves a joint study of spin-state properties of transition metal complexes by means of Density Functional Theory (DFT).

The exact functional form for DFT is not known but approximations are made through the choice of which density functional approximation (DFA) to use; this choice may depend on the chemical nature of the system and problem under study. There are a large number of studies devoted to validating functionals for accurate description of spin states. The reliability of DFT methods for giving a proper description of relative spin state energies depends largely on the functional form of the exchange functional. The OPBE functional, consisting of OPTX exchange and PBEc correlation, has shown so far excellent performance in spin-state energetics, but still it cannot be said that it is the best XC functional for spin states. Recently prof. Swart constructed a new density functional that combines the best of OPBE (spin states, reaction barriers) with the best of PBE (weak interactions) into the S12g DFA. An extensive validation study of the S12g functional is performed on nine iron complexes that show a diversity of experimentally observed spin ground states, with the discussion concerning the influence of the environment, geometry and its overall performance based on the comparison with OPBE functional. The OPBE and S12g functionals give the correct spin ground state for all investigated Fe(II) and Fe(III) complexes. Since S12g performs remarkably well it can be considered a reliable tool for studying spin state energetics in complicated transition metal systems.

This joint work has been recently published in the Journal of Serbian Chemical Society, where Prof. Swart is member of the Editorial Board. Furthermore the STSM fostered and strengthened already fruitful cooperation between the two research groups.

"Spin state relaxation of iron complexes: The case for OPBE and S12g"
M. Gruden, S. Stepanovic, and M. Swart
J. Serb. Chem. Soc. 2015, 80, 1399-1410
DOI: 10.2298/JSC150611068G
151116 151116

STSM reference: COST-STSM-CM1305-27360
STSM Participant: Maja Gruden
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