A histogram of these obtained values is given in Fig. . It shows that most of the coupling constants are small, i.e. below about 0.07 eV for κ and λ and below about 0.025 eV for SOC. While this is comparable to the TD-DFT results reported in Ref. 49, the majority of κ values are a bit larger (below about 0.12 eV) in TD-DFT. Above the mentioned values, some scattered coupling parameters do not have exact counterparts in TD-DFT. Notice that the TD-DFT results had been obtained using LC-BLYP (α = 0.2, ω = 0.08), which according to our discussion in the previous section (cf. Fig. ) shows a different composition of transitions as compared with BSE@evGW. This will have, of course, an influence on the coupling parameters, in accordance with the present findings. For instance, the MC character will be reflected in the shift of the PES. In light of the discussion of Fig. , which concluded on a more robust description of the character of transitions by BSE@evGW, the κ and λ values should be considered more reliable than the published TD-DFT ones It is interesting to ask whether the LVC model itself is applicable. The general quality of the κ and λ parameters can be estimated by comparing the resulting adiabatic PES (obtained by diagonalization of the LVC Hamiltonian) with single-point calculations for a set of geometries, displaced along particular normal modes. In Fig. respective PES cuts along mode with ξ = 25 having a frequency of 186 cm -1 are shown. It is a symmetric breathing mode meaning that a positive displacement corresponds to an elongation of the Fe-N bond lengths (results for other modes can be found in the ESI †, Fig. ).