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Kunnus, K., Vacher, M., Harlang, T. C. B., Kjaer, K. S., Haldrup, K., Biasin, E., . . . Gaffney, K. J. (2020). Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering. Nature Communications, 11(1), Article ID 634.
Open this publication in new window or tab >>Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering
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2020 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 11, no 1, article id 634Article in journal (Refereed) Published
Abstract [en]

The non-equilibrium dynamics of electrons and nuclei govern the function of photoactive materials. Disentangling these dynamics remains a critical goal for understanding photoactive materials. Here we investigate the photoinduced dynamics of the [Fe(bmip)2]2+ photosensitizer, where bmip = 2,6-bis(3-methyl-imidazole-1-ylidine)-pyridine, with simultaneous femtosecond-resolution Fe Kα and Kβ X-ray emission spectroscopy (XES) and X-ray solution scattering (XSS). This measurement shows temporal oscillations in the XES and XSS difference signals with the same 278 fs period oscillation. These oscillations originate from an Fe-ligand stretching vibrational wavepacket on a triplet metal-centered (3MC) excited state surface. This 3MC state is populated with a 110 fs time constant by 40% of the excited molecules while the rest relax to a 3MLCT excited state. The sensitivity of the Kα XES to molecular structure results from a 0.7% average Fe-ligand bond length shift between the 1 s and 2p core-ionized states surfaces.

National Category
Physical Chemistry Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-407449 (URN)10.1038/s41467-020-14468-w (DOI)000513245600024 ()32005815 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020Knut and Alice Wallenberg Foundation, KAW 2014.0370EU, European Research Council, ERCStG-259709Stiftelsen Olle Engkvist ByggmästareEuropean Regional Development Fund (ERDF), VEKOP-2.3.2-16-2017-00015Carl Tryggers foundation
Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2020-03-25Bibliographically approved
Kayser, Y., Milne, C., Juranic, P., Sala, L., Czapla-Masztafiak, J., Follath, R., . . . Szlachetkc, J. (2019). Core-level nonlinear spectroscopy triggered by stochastic X-ray pulses. Nature Communications, 10, Article ID 4761.
Open this publication in new window or tab >>Core-level nonlinear spectroscopy triggered by stochastic X-ray pulses
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2019 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 4761Article in journal (Refereed) Published
Abstract [en]

Stochastic processes are highly relevant in research fields as different as neuroscience, economy, ecology, chemistry, and fundamental physics. However, due to their intrinsic unpredictability, stochastic mechanisms are very challenging for any kind of investigations and practical applications. Here we report the deliberate use of stochastic X-ray pulses in two-dimensional spectroscopy to the simultaneous mapping of unoccupied and occupied electronic states of atoms in a regime where the opacity and transparency properties of matter are subject to the incident intensity and photon energy. A readily transferable matrix formalism is presented to extract the electronic states from a dataset measured with the monitored input from a stochastic excitation source. The presented formalism enables investigations of the response of the electronic structure to irradiation with intense X-ray pulses while the time structure of the incident pulses is preserved.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-399093 (URN)10.1038/s41467-019-12717-1 (DOI)000490982100001 ()31628306 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020
Available from: 2019-12-16 Created: 2019-12-16 Last updated: 2019-12-16Bibliographically approved
Delcey, M. G., Sörensen, L. K., Vacher, M., Couto, R. C. & Lundberg, M. (2019). Efficient calculations of a large number of highly excited states for multiconfigurational wavefunctions. Journal of Computational Chemistry, 40(19), 1789-1799
Open this publication in new window or tab >>Efficient calculations of a large number of highly excited states for multiconfigurational wavefunctions
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2019 (English)In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 40, no 19, p. 1789-1799Article in journal (Refereed) Published
Abstract [en]

Electronically excited states play important roles in many chemical reactions and spectroscopic techniques. In quantum chemistry, a common technique to solve excited states is the multiroot Davidson algorithm, but it is not designed for processes like X-ray spectroscopy that involves hundreds of highly excited states. We show how the use of a restricted active space wavefunction together with a projection operator to remove low-lying electronic states offers an efficient way to reach single and double-core-hole states. Additionally, several improvements to the stability and efficiency of the configuration interaction (CI) algorithm for a large number of states are suggested. When applied to a series of transition metal complexes the new CI algorithm does not only resolve divergence issues but also leads to typical reduction in computational time by 70%, with the largest savings for small molecules and large active spaces. Together, the projection operator and the improved CI algorithm now make it possible to simulate a wide range of single- and two-photon spectroscopies.

Place, publisher, year, edition, pages
WILEY, 2019
Keywords
configuration interaction, excited states, X-ray spectroscopy, multiconfigurational wavefunction, computational cost
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-387717 (URN)10.1002/jcc.25832 (DOI)000470013600006 ()30938847 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020Carl Tryggers foundation Stiftelsen Olle Engkvist Byggmästare
Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-06-25Bibliographically approved
Lundberg, M. & Delcey, M. G. (2019). Multiconfigurational Approach to X-ray Spectroscopy of Transition Metal Complexes. In: Ewa Broclawik; Tomasz Borowski; Mariusz Radoń (Ed.), Transition Metals in Coordination Environments: Computational chemistry and catalysis viewpoints. Springer
Open this publication in new window or tab >>Multiconfigurational Approach to X-ray Spectroscopy of Transition Metal Complexes
2019 (English)In: Transition Metals in Coordination Environments: Computational chemistry and catalysis viewpoints / [ed] Ewa Broclawik; Tomasz Borowski; Mariusz Radoń, Springer, 2019Chapter in book (Refereed)
Abstract [en]

Close correlation between theoretical modeling and experimental spectroscopy allows for identification of the electronic and geometric structure of a system through its spectral fingerprint. This is can be used to verify mechanistic proposals and is a valuable complement to calculations of reaction mechanisms using the total energy as the main criterion. For transition metal systems, X-ray spectroscopy offers a unique probe because the core-excitation energies are element specific, which makes it possible to focus on the catalytic metal. The core hole is atom-centered and sensitive to the local changes in the electronic structure, making it useful for redox active catalysts. The possibility to do time-resolved experiments also allows for rapid detection of metastable intermediates. Reliable fingerprinting requires a theoretical model that is accurate enough to distinguish between different species and multiconfigurational wavefunction approaches have recently been extended to model a number of X-ray processes of transition metal complexes. Compared to ground-state calculations, modeling of X-ray spectra is complicated by the presence of the core hole, which typically leads to multiple open shells and large effects of spin–orbit coupling. This chapter describes how these effects can be accounted for with a multiconfigurational approach and outline the basic principles and performance. It is also shown how a detailed analysis of experimental spectra can be used to extract additional information about the electronic structure.

Place, publisher, year, edition, pages
Springer, 2019
Series
Computational Chemistry and Catalysis Viewpoints, ISSN 2542-4491 ; 29
Keywords
Electronic structure - Coordination complexes - Metal–ligand bonding - Molecular orbital theory - Restricted active space
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-376635 (URN)10.1007/978-3-030-11714-6 (DOI)978-3-030-11713-9 (ISBN)978-3-030-11714-6 (ISBN)
Available from: 2019-02-07 Created: 2019-02-07 Last updated: 2019-08-08Bibliographically approved
Fernández Galván, I., Vacher, M., Alavi, A., Angeli, C., Aquilante, F., Autschbach, J., . . . Lindh, R. (2019). OpenMolcas: From Source Code to Insight. Journal of Chemical Theory and Computation, 15(11), 5925-5964
Open this publication in new window or tab >>OpenMolcas: From Source Code to Insight
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2019 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 15, no 11, p. 5925-5964Article in journal (Refereed) Published
Abstract [en]

In this Article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the new software development platform. This is followed by brief presentations of many new methods, implementations, and features of the OpenMolcas program suite. These developments include novel wave function methods such as stochastic complete active space self-consistent field, density matrix renormalization group (DMRG) methods, and hybrid multiconfigurational wave function and density functional theory models. Some of these implementations include an array of additional options and functionalities. The paper proceeds and describes developments related to explorations of potential energy surfaces. Here we present methods for the optimization of conical intersections, the simulation of adiabatic and nonadiabatic molecular dynamics, and interfaces to tools for semiclassical and quantum mechanical nuclear dynamics. Furthermore, the Article describes features unique to simulations of spectroscopic and magnetic phenomena such as the exact semiclassical description of the interaction between light and matter, various X-ray processes, magnetic circular dichroism, and properties. Finally, the paper describes a number of built-in and add-on features to support the OpenMolcas platform with postcalculation analysis and visualization, a multiscale simulation option using frozen-density embedding theory, and new electronic and muonic basis sets.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2019
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-398580 (URN)10.1021/acs.jctc.9b00532 (DOI)000497260300014 ()31509407 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation, KAW-2013.0020Swedish Research Council, 2012-3924Swedish Research Council, 2016-03398Swedish Research Council, VR 2015-03956EU, Horizon 2020, 658173EU, European Research CouncilStiftelsen Olle Engkvist ByggmästareNIH (National Institute of Health), GM126627 01German Research Foundation (DFG), BO 4915/1-1
Available from: 2019-12-09 Created: 2019-12-09 Last updated: 2019-12-09Bibliographically approved
Khamesian, M., Fernández Galván, I., Delcey, M. G., Sørensen, L. K. & Lindh, R. (2019). Spectroscopy of linear and circular polarized ligth with the exact semiclassical light–matter interaction. In: David A. Dixon (Ed.), Annual Reports in Computational Chemistry: Volume 15: (pp. 39-76). Elsevier
Open this publication in new window or tab >>Spectroscopy of linear and circular polarized ligth with the exact semiclassical light–matter interaction
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2019 (English)In: Annual Reports in Computational Chemistry: Volume 15 / [ed] David A. Dixon, Elsevier, 2019, p. 39-76Chapter in book (Refereed)
Abstract [en]

We present the theory and the analytical and numerical solution for the calculation of the oscillator and rotatory strengths of molecular systems using a state-specific formalism. For a start, this is done in the context of the exact semiclassical light–matter interaction in association with electronic wave functions expanded in a Gaussian basis. The reader is guided through the standard approximations of the field, e.g., the use of commutators, truncation of Taylor expansions, and the implications of these are discussed in parallel. Expressions for the isotropically averaged values are derived, recovering the isotropic oscillator strength in terms of the transition electric-dipole moment, and the isotropic rotatory strength in terms of the transition electric-dipole and magnetic-dipole moments. This chapter gives a detailed description of the computation of the integrals over the plane wave in association with Gaussian one-particle basis sets. Finally, a brief description is given of how the computed oscillator and rotatory strengths are related to the quantities commonly used and discussed in experimental studies.

Place, publisher, year, edition, pages
Elsevier, 2019
Series
Annual Reports in Computational Chemistry ; 15
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-398676 (URN)10.1016/bs.arcc.2019.08.004 (DOI)978-0-12-817119-6 (ISBN)
Available from: 2019-12-09 Created: 2019-12-09 Last updated: 2019-12-16Bibliographically approved
Guo, M., Sörensen, L. K., Delcey, M. G., Pinjari, R. V. & Lundberg, M. (2016). Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method. Physical Chemistry, Chemical Physics - PCCP, 4, 3250-3259
Open this publication in new window or tab >>Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method
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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
Delcey, M. G., Pedersen, T. B., Aquilante, F. & Lindh, R. (2015). Analytical gradients of the state-average complete active space self-consistent field method with density fitting. Journal of Chemical Physics, 143(4), Article ID 044110.
Open this publication in new window or tab >>Analytical gradients of the state-average complete active space self-consistent field method with density fitting
2015 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, no 4, article id 044110Article in journal (Refereed) Published
Abstract [en]

An efficient implementation of the state-averaged complete active space self-consistent field (SA-CASSCF) gradients employing density fitting (DF) is presented. The DF allows a reduction both in scaling and prefactors of the different steps involved. The performance of the algorithm is demonstrated on a set of molecules ranging up to an iron-Heme b complex which with its 79 atoms and 811 basis functions is to our knowledge the largest SA-CASSCF gradient computed. For smaller systems where the conventional code could still be used as a reference, both the linear response calculation and the gradient formation showed a clear timing reduction and the overall cost of a geometry optimization is typically reduced by more than one order of magnitude while the accuracy loss is negligible.

National Category
Theoretical Chemistry
Research subject
Chemistry with specialization in Quantum Chemistry
Identifiers
urn:nbn:se:uu:diva-243572 (URN)10.1063/1.4927228 (DOI)000358929100016 ()26233110 (PubMedID)
Funder
Swedish Research CouncileSSENCE - An eScience Collaboration
Available from: 2015-02-10 Created: 2015-02-10 Last updated: 2017-12-04Bibliographically approved
Delcey, M. G. (2015). Extending the Reach of Accurate Wavefunction Methods. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Extending the Reach of Accurate Wavefunction Methods
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Multiconfigurational quantum chemistry methods, and especially the multiconfigurational self-consistent field (MCSCF) and multireference perturbation theory (MRPT2), are powerful tools, particularly suited to the accurate modeling of photochemical processes and transition metal catalysis. However, they are limited by their high computational cost compared to other methods, especially density functional theory. Moreover, there are areas where they would be expected to perform well, but where they are not applied due to lack of experience.

This thesis addresses those issues. First, the efficiency of the Cholesky decomposition approximation to reduce the cost of MCSCF and MRPT2 without sacrificing their accuracy is demonstrated. This then motivates the extension of the Cholesky approximation to the computation of MCSCF nuclear gradients, thus strongly improving the ability to perform MCSCF non-adiabatic molecular dynamics. Typically, a tenfold speed-up is observed allowing dynamic simulation of larger systems or over longer times.

Finally, multiconfigurational methods are applied to the computation of X-ray spectra of transition metal complexes. The importance of the different parameters in the calculation is systematically investigated, laying the base for wider applications of those accurate methods in the modeling of X-ray spectroscopy. A tool to analyze the resulting spectrum in terms of molecular orbitals is also presented, strengthening the interplay between theory and experiments.

With these developments and other significant ones that have happened in recent years, multiconfigurational methods can now reach new grounds and contribute to important new discoveries

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. p. 75
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1228
Keywords
Quantum chemistry, Density fitting, CASSCF, Analytical gradients, Photochemistry, X-ray spectroscopy
National Category
Theoretical Chemistry
Research subject
Chemistry with specialization in Quantum Chemistry
Identifiers
urn:nbn:se:uu:diva-243573 (URN)978-91-554-9168-0 (ISBN)
Public defence
2015-03-31, Siegbahnsalen, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2015-03-10 Created: 2015-02-10 Last updated: 2015-04-14Bibliographically approved
Freitag, L., Knecht, S., Keller, S. F., Delcey, M. G., Aquilante, F., Pedersen, T. B., . . . Gonzalez, L. (2015). Orbital entanglement and CASSCF analysis of the Ru-NO bond in a Ruthenium nitrosyl complex. Physical Chemistry, Chemical Physics - PCCP, 17(22), 14383-14392
Open this publication in new window or tab >>Orbital entanglement and CASSCF analysis of the Ru-NO bond in a Ruthenium nitrosyl complex
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2015 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 22, p. 14383-14392Article in journal (Refereed) Published
Abstract [en]

Complete active space self-consistent field (CASSCF) wavefunctions and an orbital entanglement analysis obtained from a density-matrix renormalisation group (DMRG) calculation are used to understand the electronic structure, and, in particular, the Ru-NO bond of a Ru nitrosyl complex. Based on the configurations and orbital occupation numbers obtained for the CASSCF wavefunction and on the orbital entropy measurements evaluated for the DMRG wavefunction, we unravel electron correlation effects in the Ru coordination sphere of the complex. It is shown that Ru-NO pi bonds show static and dynamic correlation, while other Ru-ligand bonds feature predominantly dynamic correlation. The presence of static correlation requires the use of multiconfigurational methods to describe the Ru-NO bond. Subsequently, the CASSCF wavefunction is analysed in terms of configuration state functions based on localised orbitals. The analysis of the wavefunctions in the electronic singlet ground state and the first triplet state provides a picture of the Ru-NO moiety beyond the standard representation based on formal oxidation states. A distinct description of the Ru and NO fragments is advocated. The electron configuration of Ru is an equally weighted superposition of Ru-II and Ru-III configurations, with the Ru-III configuration originating from charge donation mostly from Cl ligands. However, and contrary to what is typically assumed, the electronic configuration of the NO ligand is best described as electroneutral.

National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-257054 (URN)10.1039/c4cp05278a (DOI)000355633400013 ()25767830 (PubMedID)
Available from: 2015-06-29 Created: 2015-06-29 Last updated: 2017-12-04Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9883-3569

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