uu.seUppsala University Publications
Change search
Refine search result
1 - 22 of 22
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Boström, Jonas
    et al.
    Delcey, Mickael G
    Aquilante, Francesco
    Serrano-Andrés, Luis
    Bondo Pedersen, Tomas
    Lindh, Roland
    Department of Theoretical Chemistry, Lund University.
    Calibration of Cholesky Auxiliary Basis Sets for Multiconfigurational Perturbation Theory Calculations of Excitation Energies2010In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 6, no 3, p. 747-754Article in journal (Refereed)
    Abstract [en]

    The accuracy of auxiliary basis sets derived from Cholesky decomposition of two-electron integrals is assessed for excitation energies calculated at the state-average complete active space self-consistent field (CASSCF) and multiconfigurational second order perturbation theory (CASPT2) levels of theory using segmented as well as generally contracted atomic orbital basis sets. Based on 196 valence excitations in 26 organic molecules and 72 Rydberg excitations in 3 organic molecules, the results show that Cholesky auxiliary basis sets can be used without compromising the accuracy of the multiconfigurational methods. Specifically, with a decomposition threshold of 10(-4) au, the mean error due to the Cholesky auxiliary basis set is 0.001 eV, or smaller, decreasing with increasing atomic orbital basis set quality.

  • 2. Chaudret, Robin
    et al.
    Contreras-Garcia, Julia
    Delcey, Mickaël
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Parisel, Olivier
    Yang, Weitao
    Piquemal, Jean-Philip
    Revisiting H2O Nucleation around Au+ and Hg2+: The Peculiar "Pseudo-Soft" Character of the Gold Cation2014In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 10, no 5, p. 1900-1909Article in journal (Refereed)
    Abstract [en]

    In this contribution, we propose a deeper understanding of the electronic effects affecting the nucleation of water around the Au+ and Hg2+ metal cations using quantum chemistry. To do so, and in order to go beyond usual energetical studies, we make extensive use of state of the art quantum interpretative techniques combining ELF/NCI/QTAIM/EDA computations to capture all ranges of interactions stabilizing the well characterized microhydrated structures. The Electron Localization Function (ELF) topological analysis reveals the peculiar role of the Au+ outer-shell core electrons (subvalence) that appear already spatially preorganized once the addition of the first water molecule occurs. Thus, despite the addition of other water molecules, the electronic structure of Au(H2O)(+) appears frozen due to relativistic effects leading to a maximal acceptation of only two waters in gold's first hydration shell. As the values of the QTAIM (Quantum Theory of Atoms in Molecules) cations's charge is discussed, the Non Covalent Interactions (NCI) analysis showed that Au+ appears still able to interact through longer range van der Waals interaction with the third or fourth hydration shell water molecules. As these types of interaction are not characteristic of either a hard or soft metal cation, we introduced the concept of a "pseudo-soft" cation to define Au+ behavior. Then, extending the study, we performed the same computations replacing Au+ with Hg2+, an isoelectronic cation. If Hg2+ behaves like Au+ for small water clusters, a topological, geometrical, and energetical transition appears when the number of water molecules increases. Regarding the HSAB theory, this transition is characteristic of a shift of Hg2+ from a pseudosoft form to a soft ion and appears to be due to a competition between the relativistic and correlation effects. Indeed, if relativistic effects are predominant, then mercury will behave like gold and have a similar subvalence/geometry; otherwise when correlation effects are predominant, Hg2+ behaves like a soft cation.

  • 3.
    Delcey, Mickael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Aquilante, Francesco
    Pedersen, Thomas B.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Analytical CD/RI-SA-CASSCF gradients: Implementation and performance2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Article in journal (Other academic)
  • 4.
    Delcey, Mickael G
    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.
    Vacher, Morgane
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Couto, Rafael Carvalho
    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.
    Efficient calculations of a large number of highly excited states for multiconfigurational wavefunctions2019In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 40, no 19, p. 1789-1799Article in journal (Refereed)
    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.

  • 5.
    Delcey, Mickaël G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Extending the Reach of Accurate Wavefunction Methods2015Doctoral 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

    List of papers
    1. Calibration of Cholesky Auxiliary Basis Sets for Multiconfigurational Perturbation Theory Calculations of Excitation Energies
    Open this publication in new window or tab >>Calibration of Cholesky Auxiliary Basis Sets for Multiconfigurational Perturbation Theory Calculations of Excitation Energies
    Show others...
    2010 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 6, no 3, p. 747-754Article in journal (Refereed) Published
    Abstract [en]

    The accuracy of auxiliary basis sets derived from Cholesky decomposition of two-electron integrals is assessed for excitation energies calculated at the state-average complete active space self-consistent field (CASSCF) and multiconfigurational second order perturbation theory (CASPT2) levels of theory using segmented as well as generally contracted atomic orbital basis sets. Based on 196 valence excitations in 26 organic molecules and 72 Rydberg excitations in 3 organic molecules, the results show that Cholesky auxiliary basis sets can be used without compromising the accuracy of the multiconfigurational methods. Specifically, with a decomposition threshold of 10(-4) au, the mean error due to the Cholesky auxiliary basis set is 0.001 eV, or smaller, decreasing with increasing atomic orbital basis set quality.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-141205 (URN)10.1021/ct900612k (DOI)
    Available from: 2011-01-11 Created: 2011-01-11 Last updated: 2017-12-11Bibliographically approved
    2. Analytical gradients of complete active space self-consistent field energies using Cholesky decomposition: Geometry optimization and spin-state energetics of a ruthenium nitrosyl complex
    Open this publication in new window or tab >>Analytical gradients of complete active space self-consistent field energies using Cholesky decomposition: Geometry optimization and spin-state energetics of a ruthenium nitrosyl complex
    Show others...
    2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 17, p. 174103-Article in journal (Refereed) Published
    Abstract [en]

    We present a formulation of analytical energy gradients at the complete active space self-consistent field (CASSCF) level of theory employing density fitting (DF) techniques to enable efficient geometry optimizations of large systems. As an example, the ground and lowest triplet state geometries of a ruthenium nitrosyl complex are computed at the DF-CASSCF level of theory and compared with structures obtained from density functional theory (DFT) using the B3LYP, BP86, and M06L functionals. The average deviation of all bond lengths compared to the crystal structure is 0.042 angstrom at the DF-CASSCF level of theory, which is slightly larger but still comparable with the deviations obtained by the tested DFT functionals, e. g., 0.032 angstrom with M06L. Specifically, the root-mean-square deviation between the DF-CASSCF and best DFT coordinates, delivered by BP86, is only 0.08 angstrom for S-0 and 0.11 angstrom for T-1, indicating that the geometries are very similar. While keeping the mean energy gradient errors below 0.25%, the DF technique results in a 13-fold speedup compared to the conventional CASSCF geometry optimization algorithm. Additionally, we assess the singlet-triplet energy vertical and adiabatic differences with multiconfigurational second-order perturbation theory (CASPT2) using the DF-CASSCF and DFT optimized geometries. It is found that the vertical CASPT2 energies are relatively similar regardless of the geometry employed whereas the adiabatic singlet-triplet gaps are more sensitive to the chosen triplet geometry. (C) 2014 AIP Publishing LLC.

    National Category
    Theoretical Chemistry
    Identifiers
    urn:nbn:se:uu:diva-227732 (URN)10.1063/1.4873349 (DOI)000336048000005 ()
    Available from: 2014-06-30 Created: 2014-06-30 Last updated: 2017-12-05Bibliographically approved
    3. Analytical gradients of the state-average complete active space self-consistent field method with density fitting
    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
    4. 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
    5. Cost and stability core restricted active space calculations of L-edge X-ray absorption spectra.
    Open this publication in new window or tab >>Cost and stability core restricted active space calculations of L-edge X-ray absorption spectra.
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Theoretical Chemistry
    Research subject
    Chemistry with specialization in Quantum Chemistry
    Identifiers
    urn:nbn:se:uu:diva-243570 (URN)
    Available from: 2015-02-10 Created: 2015-02-10 Last updated: 2015-03-13
    6. 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
    Download full text (pdf)
    fulltext
    Download (jpg)
    presentationsbild
    Download (pdf)
    errata
  • 6.
    Delcey, Mickaël G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Freitag, Leon
    Pedersen, Thomas Bondo
    Aquilante, Francesco
    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.
    Gonzalez, Leticia
    Analytical gradients of complete active space self-consistent field energies using Cholesky decomposition: Geometry optimization and spin-state energetics of a ruthenium nitrosyl complex2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 17, p. 174103-Article in journal (Refereed)
    Abstract [en]

    We present a formulation of analytical energy gradients at the complete active space self-consistent field (CASSCF) level of theory employing density fitting (DF) techniques to enable efficient geometry optimizations of large systems. As an example, the ground and lowest triplet state geometries of a ruthenium nitrosyl complex are computed at the DF-CASSCF level of theory and compared with structures obtained from density functional theory (DFT) using the B3LYP, BP86, and M06L functionals. The average deviation of all bond lengths compared to the crystal structure is 0.042 angstrom at the DF-CASSCF level of theory, which is slightly larger but still comparable with the deviations obtained by the tested DFT functionals, e. g., 0.032 angstrom with M06L. Specifically, the root-mean-square deviation between the DF-CASSCF and best DFT coordinates, delivered by BP86, is only 0.08 angstrom for S-0 and 0.11 angstrom for T-1, indicating that the geometries are very similar. While keeping the mean energy gradient errors below 0.25%, the DF technique results in a 13-fold speedup compared to the conventional CASSCF geometry optimization algorithm. Additionally, we assess the singlet-triplet energy vertical and adiabatic differences with multiconfigurational second-order perturbation theory (CASPT2) using the DF-CASSCF and DFT optimized geometries. It is found that the vertical CASPT2 energies are relatively similar regardless of the geometry employed whereas the adiabatic singlet-triplet gaps are more sensitive to the chosen triplet geometry. (C) 2014 AIP Publishing LLC.

  • 7.
    Delcey, Mickaël G.
    et al.
    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.
    Linguerri, R.
    Hochlaf, M.
    Francisco, J. S.
    Communication: Theoretical prediction of the structure and spectroscopic properties of the X∼ and A∼ states of hydroxymethyl peroxy (HOCH2OO) radical2013In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, no 2, p. 021105-Article in journal (Refereed)
    Abstract [en]

    The hydroxymethyl peroxy (HMOO) radical is a radical product from the oxidation of non-methane hydrocarbons. The present study provides theoretical prediction of critical spectroscopic features of this radical that should aid in its experimental characterization. Structure, rotational constants, and harmonic frequencies are presented for the ground and first excited electronic states of HMOO. The adiabatic transition energy for the A←X process is 7360 cm-1, suggesting that this transition, occurring in the mid to near infrared, is the most promising candidate for observing the radical spectroscopically. The band origin of the A←X transition of HMOO is calibrated and benchmarked with the corresponding state of the HOO radical, which is experimentally and theoretically well characterized.

  • 8.
    Delcey, Mickaël G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Pedersen, Thomas Bondo
    University of Oslo.
    Aquilante, Francesco
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Università di Bologna.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Analytical gradients of the state-average complete active space self-consistent field method with density fitting2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, no 4, article id 044110Article in journal (Refereed)
    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.

  • 9.
    Delcey, Mickaël G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Pierloot, Kristine
    Phung, Quan M.
    Vancoillie, Steven
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ryde, Ulf
    Accurate calculations of geometries and singlet-triplet energy differences for active-site models of [NiFe] hydrogenase2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 17, p. 7927-7938Article in journal (Refereed)
    Abstract [en]

    We have studied the geometry and singlet-triplet energy difference of two mono-nuclear Ni2+ models related to the active site in [NiFe] hydrogenase. Multiconfigurational second-order perturbation theory based on a complete active-space wavefunction with an active space of 12 electrons in 12 orbitals, CASPT2(12,12), reproduces experimental bond lengths to within 1 pm. Calculated singlet-triplet energy differences agree with those obtained from coupled-cluster calculations with single, double and (perturbatively treated) triple excitations (CCSD(T)) to within 12 kJ mol(-1). For a bimetallic model of the active site of [NiFe] hydrogenase, the CASPT2(12,12) results were compared with the results obtained with an extended active space of 22 electrons in 22 orbitals. This is so large that we need to use restricted active-space theory (RASPT2). The calculations predict that the singlet state is 48-57 kJ mol(-1) more stable than the triplet state for this model of the Ni-Sl(a) state. However, in the [NiFe] hydrogenase protein, the structure around the Ni ion is far from the square-planar structure preferred by the singlet state. This destabilises the singlet state so that it is only similar to 24 kJ mol(-1) more stable than the triplet state. Finally, we have studied how various density functional theory methods compare to the experimental, CCSD(T), CASPT2, and RASPT2 results. Semi-local functionals predict the best singlet-triplet energy differences, with BP86, TPSS, and PBE giving mean unsigned errors of 12-13 kJ mol(-1) (maximum errors of 25-31 kJ mol(-1)) compared to CCSD(T). For bond lengths, several methods give good results, e. g. TPSS, BP86, and M06, with mean unsigned errors of 2 pm for the bond lengths if relativistic effects are considered.

    Download full text (pdf)
    fulltext
  • 10.
    Fernández Galván, Ignacio
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Vacher, Morgane
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Alavi, Ali
    Max Planck Inst Festkorperforsch, Heisenbergstr 1, D-70569 Stuttgart, Germany.
    Angeli, Celestino
    Univ Ferrara, Dipartimento Sci Chim & Farmaceut, Via Luigi Borsari 46, I-44121 Ferrara, Italy.
    Aquilante, Francesco
    Univ Geneva, Dept Chim Phys, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.
    Autschbach, Jochen
    SUNY Buffalo, Dept Chem, Buffalo, NY 14260 USA.
    Bao, Jie J.
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Bokarev, Sergey I.
    Univ Rostock, Inst Phys, Albert Einstein Str 23-24, D-18059 Rostock, Germany.
    Bogdanov, Nikolay A.
    Max Planck Inst Festkorperforsch, Heisenbergstr 1, D-70569 Stuttgart, Germany.
    Carlson, Rebecca K.
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Chibotaru, Liviu F.
    Univ Leuven, Theory Nanomat Grp, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
    Creutzberg, Joel
    Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden;Lund Univ, Div Theoret Chem, Kemictr, POB 124, SE-22100 Lund, Sweden.
    Dattani, Nike
    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA.
    Delcey, Mickael G
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Dong, Sijia S.
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Dreuw, Andreas
    Heidelberg Univ, Interdisciplinary Ctr Sci Comp, Neuenheimer Feld 205 A, D-69120 Heidelberg, Germany.
    Freitag, Leon
    Swiss Fed Inst Technol, Lab Phys Chem, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland.
    Manuel Frutos, Luis
    Univ Alcala De Henares, Dept Quim Analit Quim Fis & Ingn Quim, E-28871 Madrid, Spain;Univ Alcala De Henares, Inst Invest Quim Andres M del Rio, E-28871 Madrid, Spain.
    Gagliardi, Laura
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Gendron, Frederic
    SUNY Buffalo, Dept Chem, Buffalo, NY 14260 USA.
    Giussani, Angelo
    UCL, Dept Chem, 20 Gordon St, London WC1H 0AJ, England;Univ Valencia, Inst Ciencia Mol, Apartado 22085, ES-46071 Valencia, Spain.
    Gonzalez, Leticia
    Univ Vienna, Inst Theoret Chem, Fac Chem, Wahringer Str 17, A-1090 Vienna, Austria.
    Grell, Gilbert
    Univ Rostock, Inst Phys, Albert Einstein Str 23-24, D-18059 Rostock, Germany.
    Guo, Meiyuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Hoyer, Chad E.
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Johansson, Marcus
    Lund Univ, Div Theoret Chem, Kemictr, POB 124, SE-22100 Lund, Sweden.
    Keller, Sebastian
    Swiss Fed Inst Technol, Lab Phys Chem, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland.
    Knecht, Stefan
    Swiss Fed Inst Technol, Lab Phys Chem, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland.
    Kovacevic, Goran
    Rudjer Boskovic Inst, Div Mat Phys, POB 180,Bijenicka 54, HR-10002 Zagreb, Croatia.
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Li Manni, Giovanni
    Max Planck Inst Festkorperforsch, Heisenbergstr 1, D-70569 Stuttgart, Germany.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ma, Yingjin
    Swiss Fed Inst Technol, Lab Phys Chem, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland.
    Mai, Sebastian
    Univ Vienna, Inst Theoret Chem, Fac Chem, Wahringer Str 17, A-1090 Vienna, Austria.
    Malhado, Joao Pedro
    Imperial Coll London, Dept Chem, London SW7 2AZ, England.
    Malmqvist, Per Ake
    Lund Univ, Div Theoret Chem, Kemictr, POB 124, SE-22100 Lund, Sweden.
    Marquetand, Philipp
    Univ Vienna, Inst Theoret Chem, Fac Chem, Wahringer Str 17, A-1090 Vienna, Austria.
    Mewes, Stefanie A.
    Heidelberg Univ, Interdisciplinary Ctr Sci Comp, Neuenheimer Feld 205 A, D-69120 Heidelberg, Germany;Massey Univ Albany, Ctr Theoret Chem & Phys, NZLAS, Private Bag 102904, Auckland 0632, New Zealand.
    Norell, Jesper
    Stockholm Univ, Dept Phys, AlbaNova Univ Ctr, SE-10691 Stockholm, Sweden.
    Olivucci, Massimo
    Univ Siena, Dept Biotechnol Chem & Pharm, Via A Moro 2, I-53100 Siena, Italy;Bowling Green State Univ, Dept Chem, Bowling Green, OH 43403 USA;Univ Strasbourg, CNRS, USIAS, F-67034 Strasbourg, France;Univ Strasbourg, CNRS, Inst Phys & Chim Mat Strasbourg, F-67034 Strasbourg, France.
    Oppel, Markus
    Univ Vienna, Inst Theoret Chem, Fac Chem, Wahringer Str 17, A-1090 Vienna, Austria.
    Phung, Quan Manh
    Pierloot, Kristine
    Katholieke Univ Leuven, Dept Chem, Celestijnenlaan 200F, B-3001 Leuven, Belgium.
    Plasser, Felix
    Loughborough Univ, Dept Chem, Loughborough LE11 3TU, Leics, England.
    Reiher, Markus
    Swiss Fed Inst Technol, Lab Phys Chem, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland.
    Sand, Andrew M.
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Schapiro, Igor
    Hebrew Univ Jerusalem, Inst Chem, Jerusalem, Israel.
    Sharma, Prachi
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Stein, Christopher J.
    Swiss Fed Inst Technol, Lab Phys Chem, Vladimir Prelog Weg 2, CH-8093 Zurich, Switzerland.
    Sörensen, Lasse Kragh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Truhlar, Donald G.
    Univ Minnesota, Dept Chem, Chem Theory Ctr, Minneapolis, MN 55455 USA;Univ Minnesota, Minnesota Supercomp Inst, Minneapolis, MN 55455 USA.
    Ugandi, Mihkel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Ungur, Liviu
    Natl Univ Singapore, Dept Chem, Singapore 117543, Singapore.
    Valentini, Alessio
    Res Unit MolSys, Theoret Phys Chem, Allee 6 Aout 11, B-4000 Liege, Belgium.
    Vancoillie, Steven
    Lund Univ, Div Theoret Chem, Kemictr, POB 124, SE-22100 Lund, Sweden.
    Veryazov, Valera
    Lund Univ, Div Theoret Chem, Kemictr, POB 124, SE-22100 Lund, Sweden.
    Weser, Oskar
    Max Planck Inst Festkorperforsch, Heisenbergstr 1, D-70569 Stuttgart, Germany.
    Wesolowski, Tomasz A.
    Univ Geneva, Dept Chim Phys, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.
    Widmark, Per-Olof
    Lund Univ, Div Theoret Chem, Kemictr, POB 124, SE-22100 Lund, Sweden.
    Wouters, Sebastian
    Brantsandpatents, Pauline van Pottelsberghelaan 24, B-9051 Sint Denijs Westrem, Belgium.
    Zech, Alexander
    Univ Geneva, Dept Chim Phys, 30 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland.
    Zobel, J. Patrick
    Lund Univ, Div Theoret Chem, Kemictr, POB 124, SE-22100 Lund, Sweden.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry. Uppsala Center for Computational Chemistry (UC3), Uppsala University, P.O. Box 596, SE-751 24 Uppsala, Sweden.
    OpenMolcas: From Source Code to Insight2019In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 15, no 11, p. 5925-5964Article in journal (Refereed)
    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.

  • 11. Freitag, Leon
    et al.
    Knecht, Stefan
    Keller, Sebastian F.
    Delcey, Mickaël G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Aquilante, Francesco
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Pedersen, Thomas Bondo
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Reiher, Markus
    Gonzalez, Leticia
    Orbital entanglement and CASSCF analysis of the Ru-NO bond in a Ruthenium nitrosyl complex2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 22, p. 14383-14392Article in journal (Refereed)
    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.

  • 12.
    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.

    Download full text (pdf)
    fulltext
  • 13.
    Kayser, Yves
    et al.
    Phys Tech Bundesanstalt, Abbestr 2-12, D-10587 Berlin, Germany;Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Milne, Chris
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Juranic, Pavle
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Sala, Leonardo
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Czapla-Masztafiak, Joanna
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.
    Follath, Rolf
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Kavcic, Matjaz
    Inst Jozef Stefan, Jamova 39, Ljubljana 1000, Slovenia.
    Knopp, Gregor
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland.
    Rehanek, Jens
    Paul Scherrer Inst, CH-5232 Villigen, Switzerland;Adv Accelerator Technol AG, CH-5234 Villigen, Switzerland.
    Blachucki, Wojciech
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.
    Delcey, Mickael G
    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.
    Tyrala, Krzysztof
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.
    Zhu, Diling
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Alonso-Mori, Roberto
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Abela, Rafael
    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.
    Szlachetkc, Jakub
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.
    Core-level nonlinear spectroscopy triggered by stochastic X-ray pulses2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 4761Article in journal (Refereed)
    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.

    Download full text (pdf)
    FULLTEXT01
  • 14.
    Khamesian, Marjan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Fernández Galván, Ignacio
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Delcey, Mickael G
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Sørensen, Lasse Kragh
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology, Stockholm, Sweden.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry. Uppsala Center of Computational Chemistry–UC3, Uppsala University, Uppsala, Sweden.
    Spectroscopy of linear and circular polarized ligth with the exact semiclassical light–matter interaction2019In: 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.

  • 15.
    Kunnus, Kristjan
    et al.
    Stanford Univ, PULSE Inst, SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA.
    Vacher, Morgane
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Harlang, Tobias C. B.
    Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden;Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Kjaer, Kasper S.
    Stanford Univ, PULSE Inst, SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA;Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden;Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Haldrup, Kristoffer
    Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Biasin, Elisa
    Stanford Univ, PULSE Inst, SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA;Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    van Driel, Tim B.
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Papai, Matyas
    Tech Univ Denmark, Dept Chem, Kemitorvet 207, DK-2800 Lyngby, Denmark.
    Chabera, Pavel
    Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden.
    Liu, Yizhu
    Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden;Lund Univ, Ctr Anal & Synth, Dept Chem, POB 12422100, Lund, Sweden.
    Tatsuno, Hideyuki
    Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden.
    Timm, Cornelia
    Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden.
    Källman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Delcey, Mickaël
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Hartsock, Robert W.
    Stanford Univ, PULSE Inst, SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA.
    Reinhard, Marco E.
    Stanford Univ, PULSE Inst, SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA.
    Koroidov, Sergey
    Stanford Univ, PULSE Inst, SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA.
    Laursen, Mads G.
    Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Hansen, Frederik B.
    Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Vester, Peter
    Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Christensen, Morten
    Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Sandberg, Lise
    Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark;Univ Copenhagen, Niels Bohr Inst, Blegdamsvej 17, DK-2100 Copenhagen, Denmark.
    Nemeth, Zoltan
    Hungarian Acad Sci, Wigner Res Ctr Phys, POB 49, H-1525 Budapest, Hungary.
    Szemes, Dorottya Sarosine
    Hungarian Acad Sci, Wigner Res Ctr Phys, POB 49, H-1525 Budapest, Hungary.
    Bajnoczi, Eva
    Hungarian Acad Sci, Wigner Res Ctr Phys, POB 49, H-1525 Budapest, Hungary.
    Alonso-Mori, Roberto
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Glownia, James M.
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Nelson, Silke
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Sikorski, Marcin
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Sokaras, Dimosthenis
    SLAC Natl Accelerator Lab, SSRL, Menlo Pk, CA 94025 USA.
    Lemke, Henrik T.
    SLAC Natl Accelerator Lab, LCLS, Menlo Pk, CA 94025 USA.
    Canton, Sophie
    ELI HU Nonprofit Ltd, ELI ALPS, H-6720 Szeged, Hungary;DESY, Notkestr 85, D-22607 Hamburg, Germany.
    Moller, Klaus B.
    Tech Univ Denmark, Dept Chem, Kemitorvet 207, DK-2800 Lyngby, Denmark.
    Nielsen, Martin M.
    Tech Univ Denmark, Dept Phys, DK-2800 Lyngby, Denmark.
    Vank, Gyorgy
    Hungarian Acad Sci, Wigner Res Ctr Phys, POB 49, H-1525 Budapest, Hungary.
    Warnmark, Kenneth
    Lund Univ, Ctr Anal & Synth, Dept Chem, POB 12422100, Lund, Sweden.
    Sundstrom, Villy
    Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden.
    Persson, Petter
    Lund Univ, Theoret Chem Div, POB 12422100, Lund, Sweden.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Uhlig, Jens
    Lund Univ, Dept Chem Phys, POB 12, S-422100 Lund, Sweden.
    Gaffney, Kelly J.
    Stanford Univ, PULSE Inst, SLAC Natl Accelerator Lab, Menlo Pk, CA 94025 USA.
    Vibrational wavepacket dynamics in Fe carbene photosensitizer determined with femtosecond X-ray emission and scattering2020In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 11, no 1, article id 634Article in journal (Refereed)
    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.

    Download full text (pdf)
    FULLTEXT01
  • 16.
    Lundberg, Marcus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Uppsala University.
    Delcey, Mickael G
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Multiconfigurational Approach to X-ray Spectroscopy of Transition Metal Complexes2019In: 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.

  • 17. Navizet, Isabelle
    et al.
    Liu, Ya-Jun
    Ferre, Nicolas
    Roca Sanjuán, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Delcey, Mickaël
    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.
    The chemistry of bioluminescence: an analysis of chemical functionalities2012In: Luminescence (Chichester, England Print), ISSN 1522-7235, E-ISSN 1522-7243, Vol. 27, no 2, p. 146-146Article in journal (Other academic)
  • 18.
    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 university.
    Lundberg, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Cost and stability core restricted active space calculations of L-edge X-ray absorption spectra.Manuscript (preprint) (Other academic)
  • 19.
    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.

    Download full text (pdf)
    fulltext
    Download full text (pdf)
    Erratum
  • 20.
    Roca Sanjuán, Daniel
    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.
    Navizet, Isabelle
    Ferre, Nicolas
    Liu, Ya-Jun
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    WARNING: The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!2012In: Luminescence (Chichester, England Print), ISSN 1522-7235, E-ISSN 1522-7243, Vol. 27, no 2, p. 155-156Article in journal (Other academic)
  • 21.
    Roca-Sanjuán, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theortical Chemistry.
    Delcey, Mickaël G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theortical Chemistry.
    Navizet, Isabelle
    Ferre, Nicolas
    Liu, Ya-Jun
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theortical Chemistry.
    Chemiluminescence and Fluorescence States of a Small Model for Coelenteramide and Cypridina Oxyluciferin: A CASSCF/CASPT2 Study2011In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 7, no 12, p. 4060-4069Article in journal (Refereed)
    Abstract [en]

    Fluorescence and chemiluminescence phenomena are often confused in experimental and theoretical studies on the luminescent properties of chemical systems. To establish the patterns that distinguish both processes, the fluorescent and chemiluminescent states of 2-acetamido-3-methylpyrazine, which is a small model of the coelenterazine/coelenteramide and Cypridina luciferin/oxyluciferin bioluminescent systems, were characterized by using the complete active space second-order perturbation (CASPT2) method. Differences in geometries and electronic structures among the states responsible for light emission were found. On the basis of the findings, some recommendations for experimental studies on chemiluminescence are suggested, and more appropriate theoretical approaches are proposed.

  • 22. Vancoillie, Steven
    et al.
    Delcey, Mickaël G.
    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.
    Vysotskiy, Victor
    Malmqvist, Per-Ake
    Veryazov, Valera
    Parallelization of a multiconfigurational perturbation theory2013In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 34, no 22, p. 1937-1948Article in journal (Refereed)
    Abstract [en]

    In this work, we present a parallel approach to complete and restricted active space second-order perturbation theory, (CASPT2/RASPT2). We also make an assessment of the performance characteristics of its particular implementation in the Molcas quantum chemistry programming package. Parallel scaling is limited by memory and I/O bandwidth instead of available cores. Significant time savings for calculations on large and complex systems can be achieved by increasing the number of processes on a single machine, as long as memory bandwidth allows, or by using multiple nodes with a fast, low-latency interconnect. We found that parallel efficiency drops below 50% when using 8-16 cores on the shared-memory architecture, or 16-32 nodes on the distributed-memory architecture, depending on the calculation. This limits the scalability of the implementation to a moderate amount of processes. Nonetheless, calculations that took more than 3 days on a serial machine could be performed in less than 5 h on an InfiniBand cluster, where the individual nodes were not even capable of running the calculation because of memory and I/O requirements. This ensures the continuing study of larger molecular systems by means of CASPT2/RASPT2 through the use of the aggregated computational resources offered by distributed computing systems.

1 - 22 of 22
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf