Magnetic coupling, interplay with spin

Alternatively, within the SOS-DFPT framework, Malkin et al. include the FC term by FPT (the SD term, which is neglected in this ansatz, has been found to be small " ). This approach has been motivated by experience with the calculation of ESR hyperfine couplings and with spin-spin coupling constants (cf. above). Based on the resulting spin-polarized Kohn-Sham orbitals, SOS-DFPT is used to account for the interplay between the external magnetic field and the spin-orbit operator. First applications include halomethanes, halomethyl cations, some other iodo compounds, and organomercury complexes. ... 

Abstract This review reports on the study of the interplay between magnetic coupling and spin transition in 2,2 -bipyrimidine (bpym)-bridged iron(II) dinuclear compounds. The coexistence of both phenomena has been observed in [Fe(bpym)(NCS)2]2(bpym), [Fe(bpym)(NCSe)2]2(bpym) and [Fe(bt)(NCS)2]2(bpym) (bpym = 2,2 -bipyrimidine, bt = 2,2 -bithiazoline) by the action of external physical perturbations such as heat, pressure or electromagnetic radiation. The competition between magnetic exchange and spin crossover has been studied in [Fe(bpym)(NCS)2]2(bpym) at 0.63 GPa. LIESST experiments carried out on [Fe(bpym)(NCSe)2]2(bpym) and [Fe(bt)(NCS)2]2(bpym) at 4.2 K have shown that it is possible to generate dinuclear molecules with different spin states in this class of compounds. A special feature of the spin crossover process in the dinuclear compounds studied so far is the plateau in the spin transition curve. Up to now, it has not been possible to explore with a microscopic physical method the nature of the species... 

In the following sections we will consider the interplay of the vibronic interaction, spin-orbital coupling and static trigonal held with regard to the problem of the magnetic properties of the low-symmetry d5-complexes. 

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