Density Functional Calculations of Electron Paramagnetic Resonance <b>g</b>- and Hyperfine-Coupling Tensors Using the Exact Two-Component (X2C) Transformation and Efficient Approximations to the Two-Electron Spin–Orbit Terms

Wodyński, Artur; Kaupp, Martin

doi:10.1021/acs.jpca.9b03979

Cited by 23 publications

(43 citation statements)

References 80 publications

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“…This may validate the previous X2C implementation for the EPR g-tensor in Ref. 77. Notably, the error introduced by neglecting the decoupling derivatives is clearly larger than the error introduced by the local approximation and the derivatives can therefore routinely be included in DLU-X2C calculations with almost no computational overhead compared to a DLU-X2C energy calculation.…”

supporting

confidence: 77%

Quasi-Relativistic Calculation of EPR g-Tensors with Derivatives of the Decoupling Transformation, Gauge-Including Atomic Orbitals, and Magnetic Balance

Franzke

2021

Preprint

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We present an exact two-component (X2C) ansatz for the EPR g-tensor using gauge-including atomic orbitals (GIAOs) and a magnetically balanced basis set expansion. In contrast to previous X2C and "fully" relativistic ansätze for the g-tensor, this implementation results in a gauge-origin invariant formalism. Furthermore, the derivatives of the relativistic decoupling matrix are considered to form the complete analytical derivative of the X2C Hamiltonian. To reduce the associated computational costs, we apply the diagonal local approximation to the unitary decoupling transformation (DLU) and the (multipole-accelerated) resolution of the identity approximation. The X2C ansatz is compared to Douglas-Kroll-Hess theory and the zeroth-order regular approximation for 11 diatomic molecules. The impact of the relativistic Hamiltonian, the basis set, and the density functional approximation is subsequently assessed for a set of 17 transition-metal complexes to complement our previous work on the hyperfine coupling constant [DOI: 10.33774/chemrxiv-2021-wnz1v-v2]. In total, 24 basis sets and 22 density functional approximations are considered. The quasi-relativistic X2C and DLU-X2C Hamiltonians accurately reproduce the results of the parent "fully" relativistic four-component theory when accounting for two-electron picture-change effects with the modified screened nuclear spin-orbit approximation in the respective one-electron integrals and integral derivatives. Generally, the uncontracted Dyall and segmented-contracted Karlsruhe x2c-type basis sets perform well when compared to large even-tempered basis sets. Moreover, (range-separated) hybrid density functional approximations are needed to match the experimental findings. Here, hybrids based on the meta -generalized gradient approximation are not an a priori improvement. Compared to the other computational parameters, the impact of the GIAOs and the magnetic balance on the actual results in standard calculations is less pronounced. Routine calculations of large molecules are possible with widely available and comparably low- cost hardware as demonstrated for [Pt(C6Cl5)4]− with 3360 basis functions and three spin-(1/2) La(II) and Lu(II) compounds. Both approaches based on a common gauge origin and GIAOs using triple- ζ basis sets lead to a good agreement with the experimental findings. The best agreement is found with hybrid functionals such as PBE0 and ωB97X-D.

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confidence: 77%

Quasi-Relativistic Calculation of EPR g-Tensors with Derivatives of the Decoupling Transformation, Gauge-Including Atomic Orbitals, and Magnetic Balance

Franzke

2021

Preprint

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“…Here, we therefore report the first quasirelativistic two-component implementation of local hybrid functionals and their comparative evaluation for the HFCs of a number of 3d, 4d, and 5d complexes. This extends a recently reported two-component implementation of HFCs and electronic g -tensors at the exact two-component (X2C) level in the Turbomole program . A main focus of our study will be the influence of respecting or violating the high-density homogeneous coordinate scaling limit for the performance of a given local hybrid or LMF.…”

Section: Introductionsupporting

confidence: 58%

Noncollinear Relativistic Two-Component X2C Calculations of Hyperfine Couplings Using Local Hybrid Functionals. Importance of the High-Density Coordinate Scaling Limit

Wodyński

Kaupp

2019

J. Chem. Theory Comput.

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Local hybrid functionals with position-dependent exact-exchange admixture have been implemented in the noncollinear spin form into a two-component X2C code and are evaluated for the hyperfine coupling tensors of a series of 3d, 4d, and 5d transition-metal complexes. One aim is to see if the potential of local hybrid functionals toward an improved balance between core−shell and valence-shell spin polarization, recently identified in nonrelativistic computations on 3d complexes (Schattenberg, C.; Maier, T. M.; Kaupp, M. J. Chem. Theory Comput. 2018, 14, 5653−5672), can be extended to the hyperfine couplings of heavier metal centers. The correctness of the two-component implementation is first established by comparison to previous computations for 3d systems with or without notable spin−orbit contributions to their hyperfine tensors, and the good performance of a standard "t-LMF" local mixing function is confirmed. However, when moving to 4d and 5d metal centers, the performance of such local mixing functions deteriorates. This is likely due to their violation of the homogeneous coordinate scaling condition in the highdensity limit, which is particularly important for the core shells of heavier atoms. A local mixing function that respects this highdensity limit performs notably better for heavier metal centers. However, it brings in much too high exact-exchange admixtures for the 3d systems and is too inflexible to simultaneously provide reasonable chemical accuracy in other areas. These results point to the ongoing need to develop improved local mixing functions and local hybrid functionals that exhibit favorable properties in different areas of space defined by very high and much lower electron densities.

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“… 87 − 89 Other benchmarking studies on 3d, 4d, and 5d transition metal complexes also converged to an optimal value of 40% exact exchange, while the choice of the pure DFT components was deemed less important. 90 , 91 A comparable approach was used recently for the calculation of EPR parameters in other LPMO enzymes. 22 , 92 …”

Section: Results and Discussionmentioning

confidence: 99%

Decoding the Ambiguous Electron Paramagnetic Resonance Signals in the Lytic Polysaccharide Monooxygenase from Photorhabdus luminescens

et al. 2022

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Understanding the structure and function of lytic polysaccharide monooxygenases (LPMOs), copper enzymes that degrade recalcitrant polysaccharides, requires the reliable atomistic interpretation of electron paramagnetic resonance (EPR) data on the Cu(II) active site. Among various LPMO families, the chitin-active Pl AA10 shows an intriguing phenomenology with distinct EPR signals, a major rhombic and a minor axial signal. Here, we combine experimental and computational investigations to uncover the structural identity of these signals. X-band EPR spectra recorded at different pH values demonstrate pH-dependent population inversion: the major rhombic signal at pH 6.5 becomes minor at pH 8.5, where the axial signal dominates. This suggests that a protonation change is involved in the interconversion. Precise structural interpretations are pursued with quantum chemical calculations. Given that accurate calculations of Cu g -tensors remain challenging for quantum chemistry, we first address this problem via a thorough calibration study. This enables us to define a density functional that achieves accurate and reliable prediction of g -tensors, giving confidence in our evaluation of Pl AA10 LPMO models. Large models were considered that include all parts of the protein matrix surrounding the Cu site, along with the characteristic second-sphere features of Pl AA10. The results uniquely identify the rhombic signal with a five-coordinate Cu ion bearing two water molecules in addition to three N-donor ligands. The axial signal is attributed to a four-coordinate Cu ion where only one of the waters remains bound, as hydroxy. Alternatives that involve decoordination of the histidine brace amino group are unlikely based on energetics and spectroscopy. These results provide a reliable spectroscopy-consistent view on the plasticity of the resting state in Pl AA10 LPMO as a foundation for further elucidating structure–property relationships and the formation of catalytically competent species. Our strategy is generally applicable to the study of EPR parameters of mononuclear copper-containing metalloenzymes.

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Density Functional Calculations of Electron Paramagnetic Resonance g- and Hyperfine-Coupling Tensors Using the Exact Two-Component (X2C) Transformation and Efficient Approximations to the Two-Electron Spin–Orbit Terms

Cited by 23 publications

References 80 publications

Quasi-Relativistic Calculation of EPR g-Tensors with Derivatives of the Decoupling Transformation, Gauge-Including Atomic Orbitals, and Magnetic Balance

Quasi-Relativistic Calculation of EPR g-Tensors with Derivatives of the Decoupling Transformation, Gauge-Including Atomic Orbitals, and Magnetic Balance

Noncollinear Relativistic Two-Component X2C Calculations of Hyperfine Couplings Using Local Hybrid Functionals. Importance of the High-Density Coordinate Scaling Limit

Decoding the Ambiguous Electron Paramagnetic Resonance Signals in the Lytic Polysaccharide Monooxygenase from Photorhabdus luminescens

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