Ŝl Ŝk 0 includes the ZFS and temperature dependent contributions to the paramagnetic chemical shifts. The ZFS dyadic Ŝl Ŝk 0 contributions in eq. 10 are evaluated in a similar fashion according to eq. 9 by neglecting the orbital Zeeman contribution to the energy Hamiltonian matrix of Ĥ ( mi ; B 0 ) operator. Consequently, Ŝl Ŝk 0 encompasses both the Curie and Van Vleck contributions, aligning with the "modified" version of the PV equation as given in ref. , whereas the "old" PV equation solely accounted for only the Curie term . The very-low temperature dependence of the diagonal Ŝl Ŝk 0 tensor components for the [Ni(AcPyOx) 3 (BPh)] + complex are shown in Fig. which is in accordance with Soncini and Van den Heuvel's report highlighting the compatibility of the "modified" PV equation with eq. 8 within a small pseudo-spin model space ( S ≤ 3/2). But as we have shown for the CoTp 2 complex later, this compatibility becomes lost as the dimension of the model space increases associated with a large ZFS.