“…These functionals and basis sets were chosen according to those that were used in publications regarding Fe 3 + , a detailed explanation of how these functionals and basis sets were chosen, is given below in section (a). The used functionals are the hybrid functional B3LYP that uses the non-local correlation, [16,17] the pure functional that uses gradient-corrected correlation PBE, [18] the functional BPW91 that is a combination of Becke exchange functional [16] (B) and the PW91 [19] correlational functional, the long-range corrected functional wB97X-D, [20] which includes empirical dispersion, and M06 L [21,22] that is a pure functional from the Truhlar group that is considered as very good for transition metals, [23] and the basis sets are TZVP [24] and the redefined Def2TZVP [25] of Ahlrichs and coworkers, aug-cc-pVTZ [26] that is a Dunning's correlation consistent basis set that includes diffuse functions, and 6-311 + + g(d,p) [27,28] that is a triple zeta all electron basis set that includes polarization and diffuse functions and is considered as very good for atoms of the two first rows of the periodic table. The SDD [29] basis set with effective core potential was used for Fe, while aug-cc-pVTZ and 6-311 + + g(d,p) were used for other atoms.…”