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  • 1.
    Blachucki, W.
    et al.
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Kayser, Y.
    Phys Tech Bundesanstalt, D-10587 Berlin, Germany.
    Czapla-Masztafiak, J.
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Juranic, P.
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Kavcic, M.
    Jozef Stefan Inst, SI-1000 Ljubljana, Slovenia.
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Knopp, G.
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Milne, C.
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Rehanek, J.
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Sá, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Szlachetko, J.
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.
    Inception of electronic damage of matter by photon-driven post-ionization mechanisms2019In: Structural Dynamics, ISSN 2329-7778, Vol. 6, no 2, article id 024901Article in journal (Refereed)
    Abstract [en]

    "Probe-before-destroy" methodology permitted diffraction and imaging measurements of intact specimens using ultrabright but highly destructive X-ray free-electron laser (XFEL) pulses. The methodology takes advantage of XFEL pulses ultrashort duration to outrun the destructive nature of the X-rays. Atomic movement, generally on the order of >50 fs, regulates the maximum pulse duration for intact specimen measurements. In this contribution, we report the electronic structure damage of a molecule with ultrashort X-ray pulses under preservation of the atoms' positions. A detailed investigation of the X-ray induced processes revealed that X-ray absorption events in the solvent produce a significant number of solvated electrons within attosecond and femtosecond timescales that are capable of coulombic interactions with the probed molecules. The presented findings show a strong influence on the experimental spectra coming from ionization of the probed atoms' surroundings leading to electronic structure modification much faster than direct absorption of photons. This work calls for consideration of this phenomenon in cases focused on samples embedded in, e.g., solutions or in matrices, which in fact concerns most of the experimental studies.

  • 2.
    Esmieu, Charlene
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. CNRS, LCC, 205 Route Narbonne,BP 44099, F-31077 Toulouse 4, France.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Redman, Holly J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Synthesis of a miniaturized [FeFe] hydrogenase model system2019In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 7, p. 2280-2284Article in journal (Refereed)
    Abstract [en]

    The reaction occurring during artificial maturation of [FeFe] hydrogenase has been recreated using molecular systems. The formation of a miniaturized [FeFe] hydrogenase model system, generated through the combination of a [4Fe4S] cluster binding oligopeptide and an organometallic Fe complex, has been monitored by a range of spectroscopic techniques. A structure of the final assembly is suggested based on EPR and FTIR spectroscopy in combination with DFT calculations. The capacity of this novel H-cluster model to catalyze H-2 production in aqueous media at mild potentials is verified in chemical assays.

  • 3.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Electronic structure investigations of transition metal complexes through X-ray spectroscopy2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Catalysts based on the first-row (3d) transition metals are commonly seen in chemical and biological reactions. To understand the role of the transition metal in the catalyst, the element specific technique core level spectroscopy is used to probe the electronic structure and geometric properties centered around the metal site. Different types of X-ray spectra can be applied to probe the metal 3d character orbitals involved in reactions, which make it possible to identify and characterize the reactive sites of samples in different forms. A detailed interpretation and understanding of the different X-ray spectra requires a unified method which can be used to model different types of X-ray spectra, e.g., soft and hard X-rays. In this thesis, theoretical investigations of the electronic structures of 3d transition metal complexes through X-ray spectroscopy are presented. The restricted active space method (RAS) is used to successfully reproduce different types of X-ray spectra by including all important spectral effects: multiplet structures, spin-orbit coupling, charge-transfer excitations, ligand field splitting and 3d-4p orbital hybridization. Different prototypes of molecules are adopted to test the applicability of the RAS theory.

    The metal L edge X-ray absorption (XAS) spectra of low spin complexes [Fe(CN)6]n and [Fe(P)(ImH)2]n in ferrous and ferric oxidation state are discussed. The RAS calculations on iron L edge spectra of these comparing complexes have been performed to fingerprint the oxidation states of metal ion, and different ligand environments. The Fe(P) system has several low-lying spin states in the ground state, which is used as a model to identify unknown species by their spectroscopic fingerprints through RAS spectra simulations. To pave the route of understanding the electronic structure of oxygen evolution complex of Mn4CaO5 cluster, the MnII(acac)2 and MnIII(acac)3 are adopted as prototypical Mn-complexes. The 3d partial fluorescence yield-XAS are employed on the Mn L-edge in solution. Combining experiments and RAS calculations, primary questions related to the oxidation state and spin state are discussed.

    The first application to simulate the metal K pre-edge XAS of mono-iron complexes and iron dimer using RAS method beyond the electric dipole is completed by implementing the approximate origin independent calculations for the intensities. The K pre-edge spectrum of centrosymmetric complex [FeCl6]n– ferrous state is discussed as s and a donor model systems. The intensity of the K pre-edge increases significantly if the centrosymmetric environment is broken, e:g:, when going from a six-coordinate to the four-coordinate site in [FeCl4]n. Distortions from centrosymmetry allow for 3d-4p orbital hybridization, which gives rise to electric dipole-allowed transitions in the K pre-edge region. In order to deliver ample electronic structure details with high resolution in the hard X-ray energy range, the two-photon 1s2p resonant inelastic X-ray scattering process is employed. Upon the above successful applications of one-photon iron L edge and K pre-edge spectra, the RAS method is extended to simulate and interpret the 1s2p resonant inelastic X-ray scattering spectra of [Fe(CN)6]n in ferrous and ferric oxidation states. The RAS applications on X-ray simulations are not restricted to the presented spectra in the thesis, it can be applied to the photon process of interest by including the corresponding core and valence orbitals of the sample.

    List of papers
    1. Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states
    Open this publication in new window or tab >>Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states
    Show others...
    2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, no 12, article id 124116Article in journal (Refereed) Published
    Abstract [en]

    The metal L-edge (2p -> 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d(5)) model systems with well-known electronic structure, viz., atomic Fe3+, high-spin [FeCl6](3-) with ligand donor bonding, and low-spin [Fe(CN)(6)](3-) that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-236075 (URN)10.1063/1.4896373 (DOI)000342844100021 ()25273421 (PubMedID)
    Note

    Correction in: Journal of Chemical Physics, vol. 141, issue 4, article number: 149905, DOI: 10.1063/1.4908043 ISI: 000349847000064

    Available from: 2014-11-12 Created: 2014-11-12 Last updated: 2017-12-05Bibliographically approved
    2. Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra
    Open this publication in new window or tab >>Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra
    Show others...
    2016 (English)In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 37, no 5, p. 477-486Article in journal (Refereed) Published
    Abstract [en]

    The restricted active-space (RAS) approach can accurately simulate metal L-edge X-ray absorption spectra of first-row transition metal complexes without the use of any fitting parameters. These characteristics provide a unique capability to identify unknown chemical species and to analyze their electronic structure. To find the best balance between cost and accuracy, the sensitivity of the simulated spectra with respect to the method variables has been tested for two models, [FeCl6](3-) and [Fe(CN)(6)](3-). For these systems, the reference calculations give deviations, when compared with experiment, of 1 eV in peak positions, 30% for the relative intensity of major peaks, and 50% for minor peaks. When compared with these deviations, the simulated spectra are sensitive to the number of final states, the inclusion of dynamical correlation, and the ionization potential electron affinity shift, in addition to the selection of the active space. The spectra are less sensitive to the quality of the basis set and even a double- basis gives reasonable results. The inclusion of dynamical correlation through second-order perturbation theory can be done efficiently using the state-specific formalism without correlating the core orbitals. Although these observations are not directly transferable to other systems, they can, together with a cost analysis, aid in the design of RAS models and help to extend the use of this powerful approach to a wider range of transition metal systems.

    Keywords
    transition metals; X-ray absorption spectroscopy; multiconfigurational wavefunction; spin-orbit coupling; charge transfer
    National Category
    Theoretical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-276263 (URN)10.1002/jcc.24237 (DOI)000369176900002 ()26502979 (PubMedID)
    Funder
    Swedish National Infrastructure for Computing (SNIC), s00112-267 liu-2012-00060-46Carl Tryggers foundation Marcus and Amalia Wallenberg FoundationSwedish Research Council
    Available from: 2016-02-10 Created: 2016-02-10 Last updated: 2017-11-30Bibliographically approved
    3. Fingerprinting electronic structures of heme using theoretical modeling of L-edge X-ray absorption spectra
    Open this publication in new window or tab >>Fingerprinting electronic structures of heme using theoretical modeling of L-edge X-ray absorption spectra
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-327409 (URN)
    Available from: 2017-08-10 Created: 2017-08-10 Last updated: 2017-08-16
    4. Probing the oxidation state: A case study of Mn II (acac) 2 and Mn III (acac) 3 on how charge and spin densities determine Mn L-edge X-ray absorption energies
    Open this publication in new window or tab >>Probing the oxidation state: A case study of Mn II (acac) 2 and Mn III (acac) 3 on how charge and spin densities determine Mn L-edge X-ray absorption energies
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-327410 (URN)
    Available from: 2017-08-10 Created: 2017-08-10 Last updated: 2017-08-16
    5. Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method
    Open this publication in new window or tab >>Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method
    Show others...
    2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 4, p. 3250-3259Article in journal (Refereed) Published
    Abstract [en]

    The intensities and relative energies of metal K pre-edge features are sensitive to both geometric and electronic structures. With the possibility to collect high-resolution spectral data it is important to find theoretical methods that include all important spectral effects: ligand-field splitting, multiplet structures, 3d-4p orbital hybridization, and charge-transfer excitations. Here the restricted active space (RAS) method is used for the first time to calculate metal K pre-edge spectra of open-shell systems, and its performance is tested against on six iron complexes: [FeCl6](n-), [FeCl4](n-), and [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. The method gives good descriptions of the spectral shapes for all six systems. The mean absolute deviation for the relative energies of different peaks is only 0.1 eV. For the two systems that lack centrosymmetry [FeCl4](2-/1-), the ratios between dipole and quadrupole intensity contributions are reproduced with an error of 10%, which leads to good descriptions of the integrated pre-edge intensities. To gain further chemical insight, the origins of the pre-edge features have been analyzed with a chemically intuitive molecular orbital picture that serves as a bridge between the spectra and the electronic structures. The pre-edges contain information about both ligand-field strengths and orbital covalencies, which can be understood by analyzing the RAS wavefunction. The RAS method can thus be used to predict and rationalize the effects of changes in both the oxidation state and ligand environment in a number of hard X-ray studies of small and medium-sized molecular systems.

    National Category
    Theoretical Chemistry
    Research subject
    Chemistry with specialization in Quantum Chemistry
    Identifiers
    urn:nbn:se:uu:diva-243571 (URN)10.1039/c5cp07487h (DOI)000369506000108 ()26742851 (PubMedID)
    Funder
    Marcus and Amalia Wallenberg FoundationSwedish Research CouncilCarl Tryggers foundation Knut and Alice Wallenberg Foundation, KAW-2013.0020Swedish National Infrastructure for Computing (SNIC), snic2013-1-317Swedish National Infrastructure for Computing (SNIC), snic2014-5-36
    Available from: 2015-02-10 Created: 2015-02-10 Last updated: 2018-08-13Bibliographically approved
    6. Applications to metal K pre-edges of transitionmetal dimers illustrate the approximate origin independence for the intensities in the length representation
    Open this publication in new window or tab >>Applications to metal K pre-edges of transitionmetal dimers illustrate the approximate origin independence for the intensities in the length representation
    2017 (English)In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 115, no 1-2, p. 174-189Article in journal (Refereed) Published
    Abstract [en]

    X-ray absorption spectroscopy (XAS) in the metal K pre-edge is a standard probe of electronic and geometric structure of transition metal complexes. Simulating the K pre-edge spectra requires contributions beyond the electric dipole, but if that term is non-zero, the second-order terms, e. g. electric quadrupoles, are no longer origin-independent. In the velocity representation, complete origin independence can be achieved by including all terms to the same order in the oscillator strength. Here, we implement that approach in the length representation and use it for restricted active space (RAS) simulations of metal K pre-edges of iron monomers and dimers. Complete origin independence is not achieved and the size of the remaining errors depends on the electric dipole oscillator strength and its ratio in length and velocity representations. The error in the origin independence is in the ANO basis sets two orders of magnitude smaller than the value of the individual contributions. For systemswith strong electric dipole contributions, the errors are not significant within 3 angstrom from a metal centre, far enough to handlemany multi-metal systems. Furthermore, we discuss the convergence of the multipole expansion, the possibility to assign spectral contributions, and the origin of negative absorption intensities. [GRAPHICS]

    Place, publisher, year, edition, pages
    TAYLOR & FRANCIS LTD, 2017
    Keywords
    Multiconfigurational wavefunction, oscillator strengths, quadrupole intensities, properties, X-ray spectroscopy
    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-319774 (URN)10.1080/00268976.2016.1225993 (DOI)000396794700015 ()
    Funder
    Knut and Alice Wallenberg Foundation, KAW-2013.0020Swedish Research Council, 2012-3910 2012-3924
    Available from: 2017-04-12 Created: 2017-04-12 Last updated: 2018-08-14Bibliographically approved
    7. Molecular orbital simulations of metal 1s2p resonant inelastic X-ray scattering
    Open this publication in new window or tab >>Molecular orbital simulations of metal 1s2p resonant inelastic X-ray scattering
    Show others...
    2016 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 120, no 29, p. 5848-5855Article in journal (Refereed) Published
    Abstract [en]

    For first-row transition metals, high-resolution 3d electronic structure information can be obtained using resonant inelastic X-ray scattering (RIXS). In the hard X-ray region, a K pre-edge (1s -> 3d) excitation can be followed by monitoring the dipole-allowed K alpha (2p -> 1s) or K beta (3p -> 1s) emission, processes labeled 1s2p or 1s3p RIXS. Here the restricted active space (RAS) approach, which is a molecular orbital method, is used for the first time to study hard X-ray RIXS processes. This is achieved by including the two sets of core orbitals in different partitions of the active space. Transition intensities are calculated using both first- and second-order expansions of the wave vector, including, but not limited to, electric dipoles and quadrupoles. The accuracy of the approach is tested for 1s2p RIXS of iron hexacyanides [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. RAS simulations accurately describe the multiplet structures and the role of 2p and 3d spin-orbit coupling on energies and selection rules. Compared to experiment, relative energies of the two [Fe(CN)(6)](3-) resonances deviate by 0.2 eV in both incident energy and energy transfer directions, and multiplet splittings in [Fe(CN)(6)](4-) are reproduced within 0.1 eV. These values are similar to what can be expected for valence excitations. The development opens the modeling of hard X-ray scattering processes for both solution catalysts and enzymatic systems.

    National Category
    Theoretical Chemistry
    Research subject
    Chemistry with specialization in Quantum Chemistry
    Identifiers
    urn:nbn:se:uu:diva-302165 (URN)10.1021/acs.jpca.6b05139 (DOI)000380730400008 ()27398775 (PubMedID)
    Funder
    Marcus and Amalia Wallenberg FoundationSwedish Research CouncilKnut and Alice Wallenberg Foundation, KAW-2013.0020
    Available from: 2016-08-31 Created: 2016-08-31 Last updated: 2017-11-21Bibliographically approved
  • 4.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Electronic structures of transition metal complexes-core level spectroscopic investigation2016Licentiate thesis, comprehensive summary (Other academic)
    List of papers
    1. Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states
    Open this publication in new window or tab >>Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states
    Show others...
    2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, no 12, article id 124116Article in journal (Refereed) Published
    Abstract [en]

    The metal L-edge (2p -> 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d(5)) model systems with well-known electronic structure, viz., atomic Fe3+, high-spin [FeCl6](3-) with ligand donor bonding, and low-spin [Fe(CN)(6)](3-) that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-236075 (URN)10.1063/1.4896373 (DOI)000342844100021 ()25273421 (PubMedID)
    Note

    Correction in: Journal of Chemical Physics, vol. 141, issue 4, article number: 149905, DOI: 10.1063/1.4908043 ISI: 000349847000064

    Available from: 2014-11-12 Created: 2014-11-12 Last updated: 2017-12-05Bibliographically approved
    2. Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra
    Open this publication in new window or tab >>Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra
    Show others...
    2015 (English)In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987XArticle in journal (Refereed) Published
    National Category
    Theoretical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-272445 (URN)
    Available from: 2016-01-13 Created: 2016-01-13 Last updated: 2017-11-30
    3. Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method
    Open this publication in new window or tab >>Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method
    Show others...
    2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 4, p. 3250-3259Article in journal (Refereed) Published
    Abstract [en]

    The intensities and relative energies of metal K pre-edge features are sensitive to both geometric and electronic structures. With the possibility to collect high-resolution spectral data it is important to find theoretical methods that include all important spectral effects: ligand-field splitting, multiplet structures, 3d-4p orbital hybridization, and charge-transfer excitations. Here the restricted active space (RAS) method is used for the first time to calculate metal K pre-edge spectra of open-shell systems, and its performance is tested against on six iron complexes: [FeCl6](n-), [FeCl4](n-), and [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. The method gives good descriptions of the spectral shapes for all six systems. The mean absolute deviation for the relative energies of different peaks is only 0.1 eV. For the two systems that lack centrosymmetry [FeCl4](2-/1-), the ratios between dipole and quadrupole intensity contributions are reproduced with an error of 10%, which leads to good descriptions of the integrated pre-edge intensities. To gain further chemical insight, the origins of the pre-edge features have been analyzed with a chemically intuitive molecular orbital picture that serves as a bridge between the spectra and the electronic structures. The pre-edges contain information about both ligand-field strengths and orbital covalencies, which can be understood by analyzing the RAS wavefunction. The RAS method can thus be used to predict and rationalize the effects of changes in both the oxidation state and ligand environment in a number of hard X-ray studies of small and medium-sized molecular systems.

    National Category
    Theoretical Chemistry
    Research subject
    Chemistry with specialization in Quantum Chemistry
    Identifiers
    urn:nbn:se:uu:diva-243571 (URN)10.1039/c5cp07487h (DOI)000369506000108 ()26742851 (PubMedID)
    Funder
    Marcus and Amalia Wallenberg FoundationSwedish Research CouncilCarl Tryggers foundation Knut and Alice Wallenberg Foundation, KAW-2013.0020Swedish National Infrastructure for Computing (SNIC), snic2013-1-317Swedish National Infrastructure for Computing (SNIC), snic2014-5-36
    Available from: 2015-02-10 Created: 2015-02-10 Last updated: 2018-08-13Bibliographically approved
    4. Molecular orbital simulations of metal 1s2p resonant inelastic X-ray scattering
    Open this publication in new window or tab >>Molecular orbital simulations of metal 1s2p resonant inelastic X-ray scattering
    Show others...
    2016 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 120, no 29, p. 5848-5855Article in journal (Refereed) Published
    Abstract [en]

    For first-row transition metals, high-resolution 3d electronic structure information can be obtained using resonant inelastic X-ray scattering (RIXS). In the hard X-ray region, a K pre-edge (1s -> 3d) excitation can be followed by monitoring the dipole-allowed K alpha (2p -> 1s) or K beta (3p -> 1s) emission, processes labeled 1s2p or 1s3p RIXS. Here the restricted active space (RAS) approach, which is a molecular orbital method, is used for the first time to study hard X-ray RIXS processes. This is achieved by including the two sets of core orbitals in different partitions of the active space. Transition intensities are calculated using both first- and second-order expansions of the wave vector, including, but not limited to, electric dipoles and quadrupoles. The accuracy of the approach is tested for 1s2p RIXS of iron hexacyanides [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. RAS simulations accurately describe the multiplet structures and the role of 2p and 3d spin-orbit coupling on energies and selection rules. Compared to experiment, relative energies of the two [Fe(CN)(6)](3-) resonances deviate by 0.2 eV in both incident energy and energy transfer directions, and multiplet splittings in [Fe(CN)(6)](4-) are reproduced within 0.1 eV. These values are similar to what can be expected for valence excitations. The development opens the modeling of hard X-ray scattering processes for both solution catalysts and enzymatic systems.

    National Category
    Theoretical Chemistry
    Research subject
    Chemistry with specialization in Quantum Chemistry
    Identifiers
    urn:nbn:se:uu:diva-302165 (URN)10.1021/acs.jpca.6b05139 (DOI)000380730400008 ()27398775 (PubMedID)
    Funder
    Marcus and Amalia Wallenberg FoundationSwedish Research CouncilKnut and Alice Wallenberg Foundation, KAW-2013.0020
    Available from: 2016-08-31 Created: 2016-08-31 Last updated: 2017-11-21Bibliographically approved
  • 5.
    Guo, Meiyuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Erik, Källman
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Sørensen, Lasse Kragh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Delcey, Mickaël G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Lawrence Berkeley Natl Lab, Div Chem Sci, Berkeley, CA 94720 USA.; Univ Calif Berkeley, Kenneth S Pitzer Ctr Theoret Chem, Dept Chem, Berkeley, CA 94720 USA.
    Pinjari, Rahul V.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. School of Chemical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, Maharashtra, India..
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Molecular orbital simulations of metal 1s2p resonant inelastic X-ray scattering2016In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 120, no 29, p. 5848-5855Article in journal (Refereed)
    Abstract [en]

    For first-row transition metals, high-resolution 3d electronic structure information can be obtained using resonant inelastic X-ray scattering (RIXS). In the hard X-ray region, a K pre-edge (1s -> 3d) excitation can be followed by monitoring the dipole-allowed K alpha (2p -> 1s) or K beta (3p -> 1s) emission, processes labeled 1s2p or 1s3p RIXS. Here the restricted active space (RAS) approach, which is a molecular orbital method, is used for the first time to study hard X-ray RIXS processes. This is achieved by including the two sets of core orbitals in different partitions of the active space. Transition intensities are calculated using both first- and second-order expansions of the wave vector, including, but not limited to, electric dipoles and quadrupoles. The accuracy of the approach is tested for 1s2p RIXS of iron hexacyanides [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. RAS simulations accurately describe the multiplet structures and the role of 2p and 3d spin-orbit coupling on energies and selection rules. Compared to experiment, relative energies of the two [Fe(CN)(6)](3-) resonances deviate by 0.2 eV in both incident energy and energy transfer directions, and multiplet splittings in [Fe(CN)(6)](4-) are reproduced within 0.1 eV. These values are similar to what can be expected for valence excitations. The development opens the modeling of hard X-ray scattering processes for both solution catalysts and enzymatic systems.

  • 6.
    Guo, Meiyuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Southwest Univ, Dept Chem & Chem Engn, Chongqing, Peoples R China.
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Pinjari, Rahul V.
    Swami Ramanand Teerth Marathwada Univ, Sch Chem Sci, Nanded, Maharashtra, India.
    Couto, Rafael Carvalho
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Sörensen, Lasse Kragh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Pierloot, Kristine
    Univ Leuven, Dept Chem, Heverlee, Belgium.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Univ Siena, Dept Biotechnol Chem & Pharm, Siena, Italy.
    Fingerprinting Electronic Structure of Heme Iron by Ab Initio Modeling of Metal L-Edge X-ray Absorption Spectra2019In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 15, no 1, p. 477-489Article in journal (Refereed)
    Abstract [en]

    The capability of the multiconfigurational restricted active space approach to identify electronic structure from spectral fingerprints is explored by applying it to iron L-edge X-ray absorption spectroscopy (XAS) of three heme systems that represent the limiting descriptions of iron in the Fe-O-2 bond, ferrous and ferric [Fe(P)(ImH)(2)](0/1+) (P = porphine, ImH = imidazole), and Fe-II(P). The level of agreement between experimental and simulated spectral shapes is calculated using the cosine similarity, which gives a quantitative and unbiased assignment. Further dimensions in fingerprinting are obtained from the L-edge branching ratio, the integrated absorption intensity, and the edge position. The results show how accurate ab initio simulations of metal L-edge XAS can complement calculations of relative energies to identify unknown species in chemical reactions.

  • 7.
    Guo, Meiyuan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Sörensen, Lasse Kragh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Delcey, Mickaël G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Pinjari, Rahul V.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 4, p. 3250-3259Article in journal (Refereed)
    Abstract [en]

    The intensities and relative energies of metal K pre-edge features are sensitive to both geometric and electronic structures. With the possibility to collect high-resolution spectral data it is important to find theoretical methods that include all important spectral effects: ligand-field splitting, multiplet structures, 3d-4p orbital hybridization, and charge-transfer excitations. Here the restricted active space (RAS) method is used for the first time to calculate metal K pre-edge spectra of open-shell systems, and its performance is tested against on six iron complexes: [FeCl6](n-), [FeCl4](n-), and [Fe(CN)(6)](n-) in ferrous and ferric oxidation states. The method gives good descriptions of the spectral shapes for all six systems. The mean absolute deviation for the relative energies of different peaks is only 0.1 eV. For the two systems that lack centrosymmetry [FeCl4](2-/1-), the ratios between dipole and quadrupole intensity contributions are reproduced with an error of 10%, which leads to good descriptions of the integrated pre-edge intensities. To gain further chemical insight, the origins of the pre-edge features have been analyzed with a chemically intuitive molecular orbital picture that serves as a bridge between the spectra and the electronic structures. The pre-edges contain information about both ligand-field strengths and orbital covalencies, which can be understood by analyzing the RAS wavefunction. The RAS method can thus be used to predict and rationalize the effects of changes in both the oxidation state and ligand environment in a number of hard X-ray studies of small and medium-sized molecular systems.

  • 8.
    Kubin, Markus
    et al.
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Berlin, Germany.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ekimova, Maria
    Max Born Inst Nichtlineare Opt & Kurzzeitspektros, Berlin, Germany.
    Baker, Michael L.
    Univ Manchester Harwell, Sch Chem, Oxon, England.
    Kroll, Thomas
    SLAG Natl Accelerator Lab, Stanford Synchrotron Radiat Lightsource, Menlo Pk, CA USA.
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Kern, Jan
    Lawrence Berkeley Natl Lab, Mol Biophys & Integrated Bioimaging Div, Berkeley, CA USA.
    Yachandra, Vittal K.
    Lawrence Berkeley Natl Lab, Mol Biophys & Integrated Bioimaging Div, Berkeley, CA USA.
    Yano, Junko
    Lawrence Berkeley Natl Lab, Mol Biophys & Integrated Bioimaging Div, Berkeley, CA USA.
    Nibbering, Erik T. J.
    Max Born Inst Nichtlineare Opt & Kurzzeitspektros, Berlin, Germany.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Wernet, Philippe
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Berlin, Germany.
    Direct Determination of Absolute Absorption Cross Sections at the L-Edge of Dilute Mn Complexes in Solution Using a Transmission Flatjet2018In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 9, p. 5449-5462Article in journal (Refereed)
    Abstract [en]

    The 3d transition metals play a pivotal role in many charge transfer processes in catalysis and biology. X-ray absorption spectroscopy at the L-edge of metal sites probes metal 2p–3d excitations, providing key access to their valence electronic structure, which is crucial for understanding these processes. We report L-edge absorption spectra of MnII(acac)2 and MnIII(acac)3 complexes in solution, utilizing a liquid flatjet for X-ray absorption spectroscopy in transmission mode. With this, we derive absolute absorption cross-sections for the L-edge transitions with peak magnitudes as large as 12 and 9 Mb for MnII(acac)2 and MnIII(acac)3, respectively. We provide insight into the electronic structure with ab initio restricted active space calculations of these L-edge transitions, reproducing the experimental spectra with excellent agreement in terms of shapes, relative energies, and relative intensities for the two complexes. Crystal field multiplet theory is used to assign spectral features in terms of the electronic structure. Comparison to charge transfer multiplet calculations reveals the importance of charge transfer in the core-excited final states. On the basis of our experimental observations, we extrapolate the feasibility of 3d transition metal L-edge absorption spectroscopy using the liquid flatjet approach in probing highly dilute biological solution samples and possible extensions to table-top soft X-ray sources.

  • 9.
    Kubin, Markus
    et al.
    Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ekimova, Maria
    Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin, Germany.
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Kern, Jan
    Lawrence Berkeley National Laboratory, Berkeley, United States.
    Yachandra, Vittal K.
    Lawrence Berkeley National Laboratory, Berkeley, United States.
    Yano, Junko
    Lawrence Berkeley National Laboratory, Berkeley, United States.
    Nibbering, Erik T. J.
    Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Berlin, Germany.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Wernet, Philippe
    Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
    Cr L-Edge X-ray Absorption Spectroscopy of CrIII(acac)3 in Solution with Measured and Calculated Absolute Absorption Cross Sections2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 29, p. 7375-7384Article in journal (Refereed)
    Abstract [en]

    X-ray absorption spectroscopy at the L-edge of 3d transition metals is widely used for probing the valence electronic structure at the metal site via 2p–3d transitions. Assessing the information contained in L-edge absorption spectra requires systematic comparison of experiment and theory. We here investigate the Cr L-edge absorption spectrum of high-spin chromium acetylacetonate CrIII(acac)3 in solution. Using a transmission flatjet enables determining absolute absorption cross sections and spectra free from X-ray-induced sample damage. We address the challenges of measuring Cr L absorption edges spectrally close to the O K absorption edge of the solvent. We critically assess how experimental absorption cross sections can be used to extract information on the electronic structure of the studied system by comparing our results of this CrIII (3d3) complex to our previous work on L-edge absorption cross sections of MnIII(acac)3 (3d4) and MnII(acac)2 (3d5). Considering our experimental uncertainties, the most insightful experimental observable for this d3(CrIII)–d4(MnIII)–d5(MnII) series is the L-edge branching ratio, and we discuss it in comparison to semiempirical multiplet theory and ab initio restricted active space calculations. We further discuss and analyze trends in integrated absorption cross sections and correlate the spectral shapes with the local electronic structure at the metal sites.

  • 10. Kubin, Markus
    et al.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Kroll, Thomas
    Lächel, Heike
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Baker, Michael L.
    Mitzner, Rolf
    Gul, Sheraz
    Kern, Jan
    Föhlisch, Alexander
    Erko, Alexei
    Bergmann, Uwe
    Yachandra, Vittal
    Yano, Junko
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Wernet, Philippe
    Probing the oxidation state of transition metal complexes: a case study on how charge and spin densities determine Mn L-edge X-ray absorption energies2018In: Chem. Sci., Vol. 9, no 33, p. 6813-6829Article in journal (Refereed)
    Abstract [en]

    Transition metals in inorganic systems and metalloproteins can occur in different oxidation states, which makes them ideal redox-active catalysts. To gain a mechanistic understanding of the catalytic reactions, knowledge of the oxidation state of the active metals, ideally in operando, is therefore critical. L-edge X-ray absorption spectroscopy (XAS) is a powerful technique that is frequently used to infer the oxidation state via a distinct blue shift of L-edge absorption energies with increasing oxidation state. A unified description accounting for quantum-chemical notions whereupon oxidation does not occur locally on the metal but on the whole molecule and the basic understanding that L-edge XAS probes the electronic structure locally at the metal has been missing to date. Here we quantify how charge and spin densities change at the metal and throughout the molecule for both redox and core-excitation processes. We explain the origin of the L-edge XAS shift between the high-spin complexes MnII(acac)2 and MnIII(acac)3 as representative model systems and use ab initio theory to uncouple effects of oxidation-state changes from geometric effects. The shift reflects an increased electron affinity of MnIII in the core-excited states compared to the ground state due to a contraction of the Mn 3d shell upon core-excitation with accompanied changes in the classical Coulomb interactions. This new picture quantifies how the metal-centered core hole probes changes in formal oxidation state and encloses and substantiates earlier explanations. The approach is broadly applicable to mechanistic studies of redox-catalytic reactions in molecular systems where charge and spin localization/delocalization determine reaction pathways.

  • 11.
    Kubin, Markus
    et al.
    Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
    Kern, Jan
    Lawrence Berkeley National Laboratory, Berkeley, USA.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Mitzner, Rolf
    Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
    Yachandra, Vittal K.
    Lawrence Berkeley National Laboratory, Berkeley, USA.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Yano, Junko
    Lawrence Berkeley National Laboratory, Berkeley, USA.
    Wernet, Philippe
    Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin, Germany.
    X-ray-induced sample damage at the Mn L-edge: a case study for soft X-ray spectroscopy of transition metal complexes in solution2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 24, p. 16817-16827Article in journal (Refereed)
    Abstract [en]

    X-ray induced sample damage can impede electronic and structural investigations of radiation-sensitive samples studied with X-rays. Here we quantify dose-dependent sample damage to the prototypical Mn-III(acac)(3) complex in solution and at room temperature for the soft X-ray range, using X-ray absorption spectroscopy at the Mn L-edge. We observe the appearance of a reduced Mn-II species as the X-ray dose is increased. We find a half-damage dose of 1.6 MGy and quantify a spectroscopically tolerable dose on the order of 0.3 MGy (1 Gy = 1 J kg(-1)), where 90% of Mn-III(acac)(3) are intact. Our dose-limit is around one order of magnitude lower than the Henderson limit (half-damage dose of 20 MGy) which is commonly employed for protein crystallography with hard X-rays. It is comparable, however, to the dose-limits obtained for collecting un-damaged Mn K-edge spectra of the photosystem II protein, using hard X-rays. The dose-dependent reduction of Mn-III observed here for solution samples occurs at a dose limit that is two to four orders of magnitude smaller than the dose limits previously reported for soft X-ray spectroscopy of iron samples in the solid phase. We compare our measured to calculated spectra from ab initio restricted active space (RAS) theory and discuss possible mechanisms for the observed dose-dependent damage of Mn-III(acac)(3) in solution. On the basis of our results, we assess the influence of sample damage in other experimental studies with soft X-rays from storage-ring synchrotron radiation sources and X-ray free-electron lasers.

  • 12.
    Liu, Tianfei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Orthaber, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Accelerating proton-coupled electron transfer of metal hydrides in catalyst model reactions2018In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 10, no 8, p. 881-887Article in journal (Refereed)
    Abstract [en]

    Metal hydrides are key intermediates in catalytic proton reduction and dihydrogen oxidation. There is currently much interest in appending proton relays near the metal centre to accelerate catalysis by proton-coupled electron transfer (PCET). However, the elementary PCET steps and the role of the proton relays are still poorly understood, and direct kinetic studies of these processes are scarce. Here, we report a series of tungsten hydride complexes as proxy catalysts, with covalently attached pyridyl groups as proton acceptors. The rate of their PCET reaction with external oxidants is increased by several orders of magnitude compared to that of the analogous systems with external pyridine on account of facilitated proton transfer. Moreover, the mechanism of the PCET reaction is altered by the appended bases. A unique feature is that the reaction can be tuned to follow three distinct PCET mechanisms-electron-first, proton-first or a concerted reaction-with very different sensitivities to oxidant and base strength. Such knowledge is crucial for rational improvements of solar fuel catalysts.

  • 13.
    Norell, Jesper
    et al.
    Stockholm Univ, Dept Phys, Stockholm, Sweden.
    Jay, Raphael
    Univ Potsdam, Inst Phys & Astron, Potsdam, Germany.
    Hantschmann, Markus
    Helmholtz Zentrum Berlin, Berlin, Germany.
    Eckert, Sebastian
    Helmholtz Zentrum Berlin, Berlin, Germany;Univ Potsdam, Inst Phys & Astron, Potsdam, Germany.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Gaffney, Kelly
    Stanford Univ, SLAC Natl Accelerator Lab, Palo Alto, CA 94304 USA.
    Wernet, Philippe
    Helmholtz Zentrum Berlin, Berlin, Germany.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Foehlisch, Alexander
    Helmholtz Zentrum Berlin, Berlin, Germany;Univ Potsdam, Inst Phys & Astron, Potsdam, Germany.
    Odelius, Michael
    Stockholm Univ, Dept Phys, Stockholm, Sweden.
    Fingerprints of electronic, spin and structural dynamics from resonant inelastic soft x-ray scattering in transient photo-chemical species2018In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Article in journal (Other academic)
  • 14.
    Norell, Jesper
    et al.
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden.
    Jay, Raphael M.
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 32, D-14476 Potsdam, Germany.
    Hantschmann, Markus
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, D-12489 Berlin, Germany.
    Eckert, Sebastian
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 32, D-14476 Potsdam, Germany;Helmholtz Zentrum Berlin Mat & Energie GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, D-12489 Berlin, Germany.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Gaffney, Kelly J.
    Stanford Univ, SLAC Natl Accelerator Lab, PULSE Inst, Menlo Pk, CA 94025 USA;SLAC Natl Accelerator Lab, Stanford Synchrotron Radiat Lightsource, Menlo Pk, CA 94025 USA.
    Wernet, Philippe
    Helmholtz Zentrum Berlin Mat & Energie GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, D-12489 Berlin, Germany.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Univ Siena, Dept Biotechnol Chem & Pharm, Via A Moro 2, I-53100 Siena, Italy.
    Foehlisch, Alexander
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 32, D-14476 Potsdam, Germany;Helmholtz Zentrum Berlin Mat & Energie GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, D-12489 Berlin, Germany.
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden.
    Fingerprints of electronic, spin and structural dynamics from resonant inelastic soft X-ray scattering in transient photo-chemical species2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 10, p. 7243-7253Article in journal (Refereed)
    Abstract [en]

    We describe how inversion symmetry separation of electronic state manifolds in resonant inelastic soft X-ray scattering (RIXS) can be applied to probe excited-state dynamics with compelling selectivity. In a case study of Fe L-3-edge RIXS in the ferricyanide complex Fe(CN)(6)(3-), we demonstrate with multi-configurational restricted active space spectrum simulations how the information content of RIXS spectral fingerprints can be used to unambiguously separate species of different electronic configurations, spin multiplicities, and structures, with possible involvement in the decay dynamics of photo-excited ligand-to-metal charge-transfer. Specifically, we propose that this could be applied to confirm or reject the presence of a hitherto elusive transient Quartet species. Thus, RIXS offers a particular possibility to settle a recent controversy regarding the decay pathway, and we expect the technique to be similarly applicable in other model systems of photo-induced dynamics.

  • 15. Pinjari, Rahul V.
    et al.
    Delcey, Mickaël G
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Odelius, Michael
    Lundberg, Marcus
    Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra2015In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987XArticle in journal (Refereed)
  • 16.
    Pinjari, Rahul V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Swami Ramanand Teerth Marathwada Univ, Sch Chem Sci, Nanded 431606, Maharashtra, India.
    Delcey, Mickaël G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra2016In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 37, no 5, p. 477-486Article in journal (Refereed)
    Abstract [en]

    The restricted active-space (RAS) approach can accurately simulate metal L-edge X-ray absorption spectra of first-row transition metal complexes without the use of any fitting parameters. These characteristics provide a unique capability to identify unknown chemical species and to analyze their electronic structure. To find the best balance between cost and accuracy, the sensitivity of the simulated spectra with respect to the method variables has been tested for two models, [FeCl6](3-) and [Fe(CN)(6)](3-). For these systems, the reference calculations give deviations, when compared with experiment, of 1 eV in peak positions, 30% for the relative intensity of major peaks, and 50% for minor peaks. When compared with these deviations, the simulated spectra are sensitive to the number of final states, the inclusion of dynamical correlation, and the ionization potential electron affinity shift, in addition to the selection of the active space. The spectra are less sensitive to the quality of the basis set and even a double- basis gives reasonable results. The inclusion of dynamical correlation through second-order perturbation theory can be done efficiently using the state-specific formalism without correlating the core orbitals. Although these observations are not directly transferable to other systems, they can, together with a cost analysis, aid in the design of RAS models and help to extend the use of this powerful approach to a wider range of transition metal systems.

  • 17.
    Pinjari, Rahul V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Delcey, Mickaël G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, no 12, article id 124116Article in journal (Refereed)
    Abstract [en]

    The metal L-edge (2p -> 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d(5)) model systems with well-known electronic structure, viz., atomic Fe3+, high-spin [FeCl6](3-) with ligand donor bonding, and low-spin [Fe(CN)(6)](3-) that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

  • 18.
    Sørensen, Lasse Kragh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Applications to metal K pre-edges of transitionmetal dimers illustrate the approximate origin independence for the intensities in the length representation2017In: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 115, no 1-2, p. 174-189Article in journal (Refereed)
    Abstract [en]

    X-ray absorption spectroscopy (XAS) in the metal K pre-edge is a standard probe of electronic and geometric structure of transition metal complexes. Simulating the K pre-edge spectra requires contributions beyond the electric dipole, but if that term is non-zero, the second-order terms, e. g. electric quadrupoles, are no longer origin-independent. In the velocity representation, complete origin independence can be achieved by including all terms to the same order in the oscillator strength. Here, we implement that approach in the length representation and use it for restricted active space (RAS) simulations of metal K pre-edges of iron monomers and dimers. Complete origin independence is not achieved and the size of the remaining errors depends on the electric dipole oscillator strength and its ratio in length and velocity representations. The error in the origin independence is in the ANO basis sets two orders of magnitude smaller than the value of the individual contributions. For systemswith strong electric dipole contributions, the errors are not significant within 3 angstrom from a metal centre, far enough to handlemany multi-metal systems. Furthermore, we discuss the convergence of the multipole expansion, the possibility to assign spectral contributions, and the origin of negative absorption intensities. [GRAPHICS]

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