Thomas Fransson
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View article: Resonant Inelastic X-ray Scattering: How Well Does LR-TDDFT Perform?
Resonant Inelastic X-ray Scattering: How Well Does LR-TDDFT Perform? Open
Resonant inelastic X-ray scattering (RIXS) is one of the most information-rich spectroscopic techniques, uniquely capable of probing excited states through their dependence on momentum, energy, and polarization. However, the inherent diffi…
View article: Attosecond inner-shell lasing at ångström wavelengths
Attosecond inner-shell lasing at ångström wavelengths Open
Since the invention of the laser, nonlinear effects such as filamentation1, Rabi cycling2,3 and collective emission4 have been explored in the optical regime, leading to a wide range of scientific and industrial applications5-8. X-ray free…
View article: X-ray Absorption Spectroscopy of Dilute Metalloenzymes at X-ray Free-Electron Lasers in a Shot-by-Shot Mode
X-ray Absorption Spectroscopy of Dilute Metalloenzymes at X-ray Free-Electron Lasers in a Shot-by-Shot Mode Open
X-ray absorption spectroscopy (XAS) of 3d transition metals provides important electronic structure information for many fields. However, X-ray-induced radiation damage under physiological temperature has prevented using this method to stu…
View article: Attosecond Inner-Shell Lasing at Angstrom Wavelengths
Attosecond Inner-Shell Lasing at Angstrom Wavelengths Open
Since the invention of the laser nonlinear effects such as filamentation, Rabi-cycling and collective emission have been explored in the optical regime leading to a wide range of scientific and industrial applications. X-ray free electron …
View article: TDDFT and the x-ray absorption spectrum of liquid water: Finding the “best” functional
TDDFT and the x-ray absorption spectrum of liquid water: Finding the “best” functional Open
We investigate the performance of time-dependent density functional theory (TDDFT) for reproducing high-level reference x-ray absorption spectra of liquid water and water clusters. For this, we apply the integrated absolute difference (IAD…
View article: TDDFT and the X-ray absorption spectrum of liquid water: finding the “best” functional
TDDFT and the X-ray absorption spectrum of liquid water: finding the “best” functional Open
We investigate the performance of time-dependent density functional theory (TDDFT) for reproducing high-level reference X-ray absorption spectra of liquid water. For this, we apply the integrated absolute difference (IAD) metric, previousl…
View article: Evaluating the Impact of the Tamm–Dancoff Approximation on X-ray Spectrum Calculations
Evaluating the Impact of the Tamm–Dancoff Approximation on X-ray Spectrum Calculations Open
The impact of the Tamm–Dancoff approximation (TDA) for time-dependent density functional theory (TDDFT) calculations of X-ray absorption and X-ray emission spectra (XAS and XES) is investigated, showing small discrepancies in the excitatio…
View article: Going around the Kok cycle of the water oxidation reaction with femtosecond X-ray crystallography
Going around the Kok cycle of the water oxidation reaction with femtosecond X-ray crystallography Open
The water oxidation reaction in photosystem II (PS II) produces most of the molecular oxygen in the atmosphere, which sustains life on Earth, and in this process releases four electrons and four protons that drive the downstream process of…
View article: Calibrating TDDFT Calculations of the X-ray Emission Spectrum of Liquid Water: The Effects of Hartree–Fock Exchange
Calibrating TDDFT Calculations of the X-ray Emission Spectrum of Liquid Water: The Effects of Hartree–Fock Exchange Open
The structure and dynamics of liquid water continue to be debated, with insight provided by, among others, X-ray emission spectroscopy (XES), which shows a split in the high-energy 1b1 feature. This split is yet to be reproduced by theory,…
View article: Structural evidence for intermediates during O2 formation in photosystem II
Structural evidence for intermediates during O2 formation in photosystem II Open
In natural photosynthesis, the light-driven splitting of water into electrons, protons and molecular oxygen forms the first step of the solar-to-chemical energy conversion process. The reaction takes place in photosystem II, where the Mn 4…
View article: Room temperature X-ray absorption spectroscopy of metalloenzymes with drop-on-demand sample delivery at XFELs
Room temperature X-ray absorption spectroscopy of metalloenzymes with drop-on-demand sample delivery at XFELs Open
X-ray crystallography and X-ray spectroscopy using X-ray free electron lasers plays an important role in understanding the interplay of structural changes in the protein and the chemical changes at the metal active site of metalloenzymes t…
View article: eChem: A Notebook Exploration of Quantum Chemistry
eChem: A Notebook Exploration of Quantum Chemistry Open
The eChem project features an e-book published as a web page (10.30746/978-91-988114-0-7), collecting a repository of Jupyter notebooks developed for the dual purpose of explaining and exploring the theory underlying computational chemistr…
View article: eChem: A notebook exploration of quantum chemistry
eChem: A notebook exploration of quantum chemistry Open
The eChem project features an e-book published as a web page https://doi.org/10.30746/978-91-988114-0-7), collecting a repository of Jupyter notebooks developed for the dual purpose of explaining and exploring the theory underlying computa…
View article: Solving Response Expressions in the ADC/ISR Framework
Solving Response Expressions in the ADC/ISR Framework Open
We present an implementation for the calculation of molecular response properties using the ADC/ISR approach up to third order. For second order ADC(2), a memory-efficient ansatz avoiding the storage of double excitation amplitudes is inve…
View article: eChem: A notebook exploration of quantum chemistry
eChem: A notebook exploration of quantum chemistry Open
The eChem project features an e-book published as a web page (https://doi.org/10.30746/ 978-91-988114-0-7), collecting a repository of Jupyter notebooks developed for the dual purpose of explaining and exploring the theory underlying compu…
View article: eChem: A notebook exploration of quantum chemistry
eChem: A notebook exploration of quantum chemistry Open
The eChem project features an e-book published as a web page (https://bit.ly/e-chem), collecting a repository of Jupyter notebooks developed for the dual purpose of explaining and exploring the underlying theory behind computational chemis…
View article: Core-hole delocalization for modeling X-ray spectroscopies: A cautionary tale
Core-hole delocalization for modeling X-ray spectroscopies: A cautionary tale Open
The influence of core-hole delocalization for X-ray photoelectron, X-ray absorption, and X-ray emission spectrum calculations is investigated in detail, using approaches including response theory, transition-potential methods, and ground s…
View article: Core–hole delocalization for modeling x-ray spectroscopies: A cautionary tale
Core–hole delocalization for modeling x-ray spectroscopies: A cautionary tale Open
The influence of core–hole delocalization for x-ray photoelectron, x-ray absorption, and x-ray emission spectrum calculations is investigated in detail using approaches including response theory, transition-potential methods, and ground st…
View article: Using core-hole reference states for calculating X-ray photoelectron and emission spectra
Using core-hole reference states for calculating X-ray photoelectron and emission spectra Open
For the calculation of core-ionization energies (IE), X-ray photoelectron spectroscopy (XPS), and X-ray emission spectroscopy (XES), a commonly applied approach is to use non-Aufbau reference states with a core-hole as either final (IE and…
View article: Core-hole delocalization for modeling X-ray spectroscopies: A cautionary tale
Core-hole delocalization for modeling X-ray spectroscopies: A cautionary tale Open
The influence of core-hole delocalization for X-ray photoelectron, X-ray absorption, and X-ray emission spectrum calculations is investigated in detail, using approaches including response theory, transition-potential methods, and ground s…
View article: Using core-hole reference states for calculating X-ray photoelectron and emission spectra
Using core-hole reference states for calculating X-ray photoelectron and emission spectra Open
For the calculation of core-ionization energies (IE), X-ray photoelectron spectroscopy (XPS), and X-ray emission spectroscopy (XES), a commonly applied approach is to use non-Aufbau reference states with a core-hole as either final (IE and…
View article: Using core-hole reference states for calculating X-ray photoelectron and emission spectra
Using core-hole reference states for calculating X-ray photoelectron and emission spectra Open
A protocol for removing near-singularities in post-HF calculations of core-ionization energies and X-ray emission spectra is presented, enabling highly reliable calculations of such properties for large molecules and when using large basis…
View article: Effects of x-ray free-electron laser pulse intensity on the Mn K<b><i>β</i></b><sub>1,3</sub> x-ray emission spectrum in photosystem II—A case study for metalloprotein crystals and solutions
Effects of x-ray free-electron laser pulse intensity on the Mn K<b><i>β</i></b><sub>1,3</sub> x-ray emission spectrum in photosystem II—A case study for metalloprotein crystals and solutions Open
In the last ten years, x-ray free-electron lasers (XFELs) have been successfully employed to characterize metalloproteins at room temperature using various techniques including x-ray diffraction, scattering, and spectroscopy. The approach …
View article: X-ray free-electron laser studies reveal correlated motion during isopenicillin <i>N</i> synthase catalysis
X-ray free-electron laser studies reveal correlated motion during isopenicillin <i>N</i> synthase catalysis Open
Complementary XFEL methods reveal O 2 reaction intermediates and global protein dynamics during Isopenicillin N synthase catalysis.
View article: Gator: A Python‐driven program for spectroscopy simulations using correlated wave functions
Gator: A Python‐driven program for spectroscopy simulations using correlated wave functions Open
The Gator program has been developed for computational spectroscopy and calculations of molecular properties using real and complex propagators at the correlated level of wave function theory. Currently, the focus lies on methods based on …
View article: XABOOM: An X-ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π* Transitions
XABOOM: An X-ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π* Transitions Open
The performance of several standard and popular approaches for calculating X-ray absorption spectra at the carbon, nitrogen, and oxygen K-edges of 40 primarily organic molecules up to the size of guanine has been evaluated, focusing on the…
View article: XABOOM: An X-Ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π ∗ Transitions
XABOOM: An X-Ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π ∗ Transitions Open
Presenting a benchmark study on calculating X-ray absorption spectra, named XABOOM (X-ray absorption benchmark of organic molecules), comparing the performance for considering 1s → π ∗ transitions using ADC, CC, TDDFT, and TP-DFT. Molecula…