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  • 1.
    da Cruz, Vinicius Vaz
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Ignatova, Nina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Couto, Rafael C.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Fedotov, Daniil A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Siberian Fed Univ, Krasnoyarsk 660041, Russia..
    Rehn, Dirk R.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Savchenko, Viktoriia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Polyutov, Sergey
    Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Niskanen, Johannes
    Univ Turku, Dept Phys & Astron, FI-20014 Turun, Finland.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Eckert, Sebastian
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Jay, Raphael M.
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Fondell, Mattis
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Schmitt, Thorsten
    Paul Scherrer Inst, Photon Sci Div, CH-5232 Villigen, Switzerland..
    Pietzsch, Annette
    Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Foehlisch, Alexander
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Gel'mukhanov, Faris
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Odelius, Michael
    Stockholm Univ, AlbaNova Univ Ctr, Dept Phys, S-10691 Stockholm, Sweden..
    Kimberg, Victor
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Siberian Fed Univ, Krasnoyarsk 660041, Russia.;Fed Res Ctr KSC SB RAS, Kirensky Inst Phys, Krasnoyarsk 660036, Russia..
    Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol2019Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, nr 23, artikkel-id 234301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a combined theoretical and experimental study of core-excitation spectra of gas and liquid phase methanol as obtained with the use of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The electronic transitions are studied with computational methods that include strict and extended second-order algebraic diagrammatic construction [ADC(2) and ADC(2)-x], restricted active space second-order perturbation theory, and time-dependent density functional theory-providing a complete assignment of the near oxygen K-edge XAS. We show that multimode nuclear dynamics is of crucial importance for explaining the available experimental XAS and RIXS spectra. The multimode nuclear motion was considered in a recently developed "mixed representation" where dissociative states and highly excited vibrational modes are accurately treated with a time-dependent wave packet technique, while the remaining active vibrational modes are described using Franck-Condon amplitudes. Particular attention is paid to the polarization dependence of RIXS and the effects of the isotopic substitution on the RIXS profile in the case of dissociative core-excited states. Our approach predicts the splitting of the 2a RIXS peak to be due to an interplay between molecular and pseudo-atomic features arising in the course of transitions between dissociative core- and valence-excited states. The dynamical nature of the splitting of the 2a peak in RIXS of liquid methanol near pre-edge core excitation is shown. The theoretical results are in good agreement with our liquid phase measurements and gas phase experimental data available from the literature.

  • 2. Fransson, Thomas
    et al.
    Rehn, Dirk Robert
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Dreuw, Andreas
    Norman, P.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Static polarizabilities and C-6 dispersion coefficients using the algebraic-diagrammatic construction scheme for the complex polarization propagator2017Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, nr 9, artikkel-id 094301Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An implementation of the damped linear response function, or complex polarization propagator, using the algebraic-diagrammatic construction (ADC) scheme has been developed and utilized for the calculation of electric-dipole polarizabilities and C-6 dispersion coefficients. Four noble gases (He, Ne, Ar, and Kr), five n-alkanes (methane, ethane, propane, butane, and pentane), three carbonyls (formaldehyde, acetaldehyde, and acetone), and three unsaturated hydrocarbons (ethene, acetylene, and benzene) have been treated with the hierarchical set of models ADC(2), ADC(2)-x, and ADC(3/2), and comparison has been made to results obtained with damped linear response Hartree-Fock (HF) and coupled cluster singles and doubles (CCSD) theory as well as high-quality experimental estimates via the dipole oscillator strength distribution approach. This study marks the first ADC calculations of C-6 dispersion coefficients and the first ADC(3/2) calculations of static polarizabilities. Results at CCSD and ADC(3/2) levels of theory are shown to be of similar quality, with electron correlation effects increasing the molecular property values for all calculations except CCSD considerations of ethene and acetylene (attributed to an overestimation of bond electron density at HF level of theory). The discrepancies betweenCCSDand ADC(3/2) are partially due toADCoverestimating anisotropies, and discrepancies with respect to experimental values are partially due to the lack of zero-point vibrational effects in the present study.

  • 3. Hodecker, M.
    et al.
    Rehn, Dirk Robert
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Dreuw, A.
    Algebraic-diagrammatic construction scheme for the polarization propagator including ground-state coupled-cluster amplitudes. II. Static polarizabilities2019Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, nr 17, artikkel-id 174105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The modification of the algebraic-diagrammatic construction (ADC) scheme for the polarization propagator using ground-state coupled-cluster (CC) instead of Møller-Plesset (MP) amplitudes, referred to as CC-ADC, is extended to the calculation of molecular properties, in particular, dipole polarizabilities. Furthermore, in addition to CC with double excitations (CCD), CC with single and double excitations (CCSD) amplitudes can be used, also in the second-order transition moments of the ADC(3/2) method. In the second-order CC-ADC(2) variants, the MP correlation coefficients occurring in ADC are replaced by either CCD or CCSD amplitudes, while in the F/CC-ADC(2) and F/CC-ADC(3/2) variants, they are replaced only in the second-order modified transition moments. These newly implemented variants are used to calculate the static dipole polarizability of several small- to medium-sized molecules, and the results are compared to the ones obtained by full configuration interaction or experiment. It is shown that the results are consistently improved by the use of CC amplitudes, in particular, for aromatic systems such as benzene or pyridine, which have proven to be difficult cases for standard ADC approaches. In this case, the second-order CC-ADC(2) and F/CC-ADC(2) variants yield significantly better results than the standard third-order ADC(3/2) method, at a computational cost amounting to only about 1% of the latter.

  • 4. Orms, Natalie
    et al.
    Rehn, Dirk R.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Dreuw, Andreas
    Krylov, Anna I.
    Characterizing Bonding Patterns in Diradicals and Triradicals by Density-Based Wave Function Analysis: A Uniform Approach2018Inngår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 14, nr 2, s. 638-648Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Density-based wave function analysis enables unambiguous comparisons of the electronic structure computed by different methods and removes ambiguity of orbital choices. We use this tool to investigate the performance of different spin flip methods for several prototypical diradicals and triradicals. In contrast to previous calibration studies that focused on energy gaps between high- and low spin-states, we focus on the properties of the underlying wave functions, such as the number of effectively unpaired electrons. Comparison of different density functional and wave function theory results provides insight into the performance of the different methods when applied to strongly correlated systems such as polyradicals. We show that canonical molecular orbitals for species like large copper-containing diradicals fail to correctly represent the underlying electronic structure due to highly non-Koopmans character, while density-based analysis of the same wave function delivers a clear picture of the bonding pattern.

  • 5.
    Rehn, Dirk Robert
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Dreuw, Andreas
    Norman, Patrick
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Resonant Inelastic X-ray Scattering Amplitudes and Cross Sections in the Algebraic Diagrammatic Construction/Intermediate State Representation (ADC/ISR) Approach2017Inngår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 13, nr 11, s. 5552-5559Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A scheme has been derived and implemented to gain computational access to the full electronic part of the Kramers-Heisenberg-Dirac (KHD) expression for resonant and nonresonant inelastic scattering amplitudes. Our implementation of this scheme is based on the complex polarization propagator in the algebraic diagrammatic construction (ADC) framework and within its intermediate state representation (ISR). The hierarchy of the second- and third-order ADC/ISR computational schemes known as ADC(2), ADC(2)-x, and ADC(3/2) is considered, and the calculated resonant inelastic X-ray scattering (RIXS) amplitudes and transition strengths for water are in excellent agreement with recent experimental data.

  • 6.
    Vaz da Cruz, Vinicius
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. KTH.
    Ignatova, Nina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Carvalho Couto, Rafael
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Fedotov, Daniil
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Robert Rehn, Dirk
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Savchenko, Viktoriia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Norman, Patrick
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Polyutov, Sergey
    Niskanen, Johannes
    Fondell, Mattis
    Eckert, Sebastian
    Jay, Raphael
    Schmitt, Thorsten
    Pietzsch, Annette
    Föhlisch, Alexander
    Gel'mukhanov, Faris
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Odelius, Michael
    Kimberg, Victor
    Resonant inelastic X-ray scattering and X-ray absorption of methanol at the near oxygen K-edgeManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We report on a theoretical analysis of core-excitation spectra of gas and liquid phase methanol asobtained with use of X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering(RIXS). The electronic transitions are studied with complementary computational methods includ-ing strict and extended second-order algebraic diagrammatic construction (ADC(2) and ADC(2)-x),restricted active space second-order perturbation theory (RASPT2), and time-dependent densityfunctional theory (TDDFT)—providing a complete assignment of the near oxygen K-edge XAS.We show that multimode nuclear dynamics is of crucial importance for explaining the availableexperimental XAS and RIXS spectra. Multimode nuclear motions was considered in a developedmixed representation where dissociative states and highly excited vibrational modes are accuratelytreated with a time-dependent wave packet technique while the remaining active vibrational modesare described using Franck–Condon amplitudes. Particular attention is paid to the polarizationdependence of RIXS and the effects of the isotope substitution on the RIXS profile in the case ofdissociative core-excited states. Our approach predicts the splitting of the 2a RIXS peak to bedue to an interplay between molecular and atomic-like features arising in the course of transitionsbetween dissociative core- and valence-excited states. The dynamical nature of the splitting of the2a peak in RIXS of liquid methanol near pre-edge core excitation is shown. The theoretical resultsare in good agreement with available experimental data.

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