Exploring the applicability of density functional tight binding to transition metal ions. Parameterization for nickel with the spin‐polarized DFTB3 model

Abstract

In this work, we explore the applicability and limitations of the current third order density functional tight binding (DFTB3) formalism for treating transition metal ions using nickel as an example. To be consistent with recent parameterization of DFTB3 for copper, the parametrization for nickel is conducted in a spinpolarized formulation and with orbital-resolved Hubbard parameters and their charge derivatives. The performance of the current parameter set is evaluated based on structural and energetic properties of a set of nickel-containing compounds that involve biologically relevant ligands. Qualitatively similar to findings in previous studies of copper complexes, the DFTB3 results are more reliable for nickel complexes with neutral ligands than for charged ligands; nevertheless, encouraging agreement is noted in comparison to the reference method, B3LYP/aug-cc-pVTZ, especially for structural properties, including cases that exhibit Jahn-Teller distortions; the structures also compare favorably to available X-ray data in the Cambridge Crystallographic Database for a number of nickel-containing compounds. As to limitations, we find it is necessary to use different d shell Hubbard charge derivatives for Ni(I) and Ni(II), due to the distinct electronic configurations for the nickel ion in the respective complexes, and substantial errors are observed for ligand binding energies, especially for charged ligands, d orbital splitting energies and splitting between singlet and triplet spin states for Ni(II) compounds. These observations highlight that future improvement in intra-d correlation and ligand polarization is required to enable the application of the DFTB3 model to complex transition metal ions.

Dealing with Spin States in Computational Organometallic Catalysis

“…[103][104][105][106] Until recently, no straightforward parameterization for transition-metals was available, but a recent study for nickel based on DFTB3 showed the feasibility of such an approach. [107] The resulting DFTB structures for a number of nickel complexes compare favorably to available X-ray structures, and an encouraging agreement with the B3LYP/aug-cc-pVTZ reference data was observed.…”

GFN2-xTB - an Accurate and Broadly Parametrized Self-Consistent Tight-Binding Quantum Chemical Method with Multipole Electrostatics and Density-Dependent Dispersion Contributions

“…The highest-level variant (DFTB3) employs a selfconsistent charge treatment including up to third order density fluctuation terms 55,56 and has been parametrized for a number of chemical elements. [58][59][60][61][62] In particular, the element pair-specific parametrization used in all aforementioned methods has complicated the parametrization procedure and only PM6 covers large parts of the periodic table of elements (70 elements). Recently, we have presented a DFTB3 variant, termed GFN-xTB, which mostly follows a global and element-specific parameters only strategy and is parametrized to all elements through radon.…”

Probing the Suitability of Different Ca2+ Parameters for Long Simulations of Diisopropyl Fluorophosphatase

“…DFTB3 was previously shown to produce good geometries and adequate energy for a wide range of scenarios. It performed well for biomolecular systems [ 61 , 62 , 63 ], systems with metal cations in general [ 29 , 64 , 65 , 66 ], and Ca 2+ specifically [ 67 , 68 ], achieving better energies then DFT calculations with a double-ζ basis set. In both tasks, QM simulation was run in parallel by 10 walkers each sampling for 100 ps thus accumulating 1 ns of QM/MM trajectory.…”