Zero-field splitting in nickel(II) complexes: A comparison of DFT and multi-configurational wavefunction calculations

Abstract

A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu The Journal of Chemical Physics 132, 154104 (2010) The zero-field splitting (ZFS) is an important quantity in the electron spin Hamiltonian for S = 1 or higher. We report calculations of the ZFS in some six-and five-coordinated nickel(II) complexes (S = 1), using different levels of theory within the framework of the ORCA program package [F. Neese, Wiley Interdiscip. Rev.: Comput. Mol. Sci. 2, 73 (2012)]. We compare the high-end ab initio calculations (complete active space self-consistent field and n-electron valence state perturbation theory), making use of both the second-order perturbation theory and the quasi-degenerate perturbation approach, with density functional theory (DFT) methods using different functionals. The pattern of results obtained at the ab initio levels is quite consistent and in reasonable agreement with experimental data. The DFT methods used to calculate the ZFS give very strongly functional-dependent results and do not seem to function well for our systems.

Magnetic Anisotropy of Mononuclear NiII Complexes: On the Importance of Structural Diversity and the Structural Distortions

“…17, 32 Although the density functional calculations are widely used for the estimation of zfs parameters for polynuclear complexes,33 generally the computed zfs parameters are less accurate compared with ab initio treatment 1c. 20, 26…”

“…Despite the increased number of Ni II ‐based SMMs since the first report,19a the electronic or structural origin of zfs in various types of Ni II complexes still remain unexplored 9a. 26, 27 Based on ligand‐field theory, Abragam and Bleaney proposed the following qualitative equation [Eq (1)] for the D values in Ni II complexes, in which λ =spin–orbit coupling constant Δ =crystal field splitting parameter: …”

“…To offer a clear‐cut understanding of zfs in varied coordination environments and to ascertain the factors on which the sign and magnitude of this parameter depend, herein we have undertaken detailed ab initio calculations of zfs parameters in a series of mononuclear Ni II complexes. We have also developed magneto–structural D correlations to offer clues on how to enhance the zfs further in a given coordination environment for a Ni II complexes 26…”

Ab initio paramagnetic NMR shifts via point-dipole approximation in a large magnetic-anisotropy Co(ii) complex

“…All the 10 quartet roots as well as 15 doublets possible within this active space were included. It has been shown 9,15,38,39 that this methodology gives good results for the EPR parameters including the critical ZFS tensor, for systems with two or more unpaired electrons. a Optimised bond lengths, see illustration of the structure in Fig.…”

“…It has been seen before 9,15,38 that the geometry of the paramagnetic center can dramatically influence the resulting ZFS and g-tensors. Table 1 shows the effect of the detailed structure as optimised using the PBE and PBE0 functionals, with particularly the PBE0 functional being not only first-principles-based but also performing well for structures of transition metal complexes.…”