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Your search keyword '"Norman, Patrick A."' showing total 77 results
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77 results on '"Norman, Patrick A."'

1. Solving response expressions in the ADC/ISR framework

Author

Scheurer, Maximilian, Papapostolou, Antonia, Fransson, Thomas, Norman, Patrick, Dreuw, Andreas, Rehn, Dirk R., Scheurer, Maximilian, Papapostolou, Antonia, Fransson, Thomas, Norman, Patrick, Dreuw, Andreas, and Rehn, Dirk R.

Abstract

We present an implementation for the calculation of molecular response properties using the algebraic-diagrammatic construction (ADC)/intermediate state representation approach. For the second-order ADC model [ADC(2)], a memory-efficient ansatz avoiding the storage of double excitation amplitudes is investigated. We compare the performance of different numerical algorithms for the solution of the underlying response equations for ADC(2) and show that our approach also strongly improves the convergence behavior for the investigated algorithms compared with the standard implementation. All routines are implemented in an open-source Python library., QC 20230404

Published
2023
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3. Simulations of x-ray absorption spectra for CO desorbing from Ru(0001) with transition-potential and time-dependent density functional theory approaches

Author

Rodrigues, Gabriel L. S., Diesen, Elias, Voss, Johannes, Norman, Patrick, Pettersson, Lars G. M., Rodrigues, Gabriel L. S., Diesen, Elias, Voss, Johannes, Norman, Patrick, and Pettersson, Lars G. M.

Abstract

The desorption of a carbon monoxide molecule from a Ru(0001) surface was studied by means of X-ray Absorption Spectra (XAS) computed with Transition Potential (TP-DFT) and Time Dependent (TD-DFT) DFT methods. By unraveling the evolution of the CO electronic structure upon desorption, we observed that at 2.3 & ANGS; from the surface, the CO molecule has already predominantly gas-phase character. While C 1s XAS is quite insensitive to changes in the C-O bond length, the O 1s excitation is very sensitive with the pi* coming down in energy upon CO bond stretching, which competes with the increase in orbital energy due to the repulsive interaction with the metallic surface. We show in a systematic way that the TP-DFT method can describe the XAS rather well at the endpoints (chemisorbed and gas phase) but is affected by artificial charge transfer and/or incorrect spin treatment in the transition region in cases like CO, where there are low-lying pi* orbitals and large exchange interactions between the core 1s and valence-acceptor pi* orbitals. As an alternative, we demonstrate by comparing with experimental data that a linear response approach using TD-DFT employing common exchange-correlation functionals and finite-size clusters can yield a good description of the spectral evolution of the 1s & RARR; pi* transition with correct spin and gas-to-chemisorbed chemical shifts in good agreement with experiment., QC 20220208

Published
2022
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6. Hydrogen bond effects in multimode nuclear dynamics of acetic acid observed via resonant x-ray scattering

Author

Savchenko, Viktoriia, primary, Ekholm, Victor, additional, Brumboiu, Iulia Emilia, additional, Norman, Patrick, additional, Pietzsch, Annette, additional, Föhlisch, Alexander, additional, Rubensson, Jan-Erik, additional, Gråsjö, Johan, additional, Björneholm, Olle, additional, Såthe, Conny, additional, Dong, Minjie, additional, Schmitt, Thorsten, additional, McNally, Daniel, additional, Lu, Xingye, additional, Krasnov, Pavel, additional, Polyutov, Sergey P., additional, Gel’mukhanov, Faris, additional, Odelius, Michael, additional, and Kimberg, Victor, additional

Published
2021
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7. Hydrogen bond effects in multimode nuclear dynamics of acetic acid observed via resonant x-ray scattering

Author

Savchenko, Viktoriia, Ekholm, Victor, Brumboiu, Iulia Emilia, Norman, Patrick, Pietzsch, Annette, Foehlisch, Alexander, Rubensson, Jan-Erik, Gråsjö, Johan, Björneholm, Olle, Sathe, Conny, Dong, Minjie, Schmitt, Thorsten, McNally, Daniel, Lu, Xingye, Krasnov, Pavel, Polyutov, Sergey P., Gel'mukhanov, Faris, Odelius, Michael, Kimberg, Victor, Savchenko, Viktoriia, Ekholm, Victor, Brumboiu, Iulia Emilia, Norman, Patrick, Pietzsch, Annette, Foehlisch, Alexander, Rubensson, Jan-Erik, Gråsjö, Johan, Björneholm, Olle, Sathe, Conny, Dong, Minjie, Schmitt, Thorsten, McNally, Daniel, Lu, Xingye, Krasnov, Pavel, Polyutov, Sergey P., Gel'mukhanov, Faris, Odelius, Michael, and Kimberg, Victor

Abstract

A theoretical and experimental study of the gas phase and liquid acetic acid based on resonant inelastic x-ray scattering (RIXS) spectroscopy is presented. We combine and compare different levels of theory for an isolated molecule for a comprehensive analysis, including electronic and vibrational degrees of freedom. The excitation energy scan over the oxygen K-edge absorption reveals nuclear dynamic effects in the core-excited and final electronic states. The theoretical simulations for the monomer and two different forms of the dimer are compared against high-resolution experimental data for pure liquid acetic acid. We show that the theoretical model based on a dimer describes the hydrogen bond formation in the liquid phase well and that this bond formation sufficiently alters the RIXS spectra, allowing us to trace these effects directly from the experiment. Multimode vibrational dynamics is accounted for in our simulations by using a hybrid time-dependent stationary approach for the quantum nuclear wave packet simulations, showing the important role it plays in RIXS.

Published
2021
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8. Analytical gradients for core-excited states in the algebraic diagrammatic construction (ADC) framework

Author

Brumboiu, Iulia E., Rehn, Dirk R., Dreuw, Andreas, Rhee, Young Min, Norman, Patrick, Brumboiu, Iulia E., Rehn, Dirk R., Dreuw, Andreas, Rhee, Young Min, and Norman, Patrick

Abstract

Expressions for analytical molecular gradients of core-excited states have been derived and implemented for the hierarchy of algebraic diagrammatic construction (ADC) methods up to extended second-order within the core-valence separation (CVS) approximation. We illustrate the use of CVS-ADC gradients by determining relaxed core-excited state potential energy surfaces and optimized geometries for water, formic acid, and benzene. For water, our results show that in the dissociative lowest core-excited state, a linear configuration is preferred. For formic acid, we find that the O K-edge lowest core-excited state is non-planar, a fact that is not captured by the equivalent core approximation where the core-excited atom with its hole is replaced by the "Z + 1" neighboring atom in the periodic table. For benzene, the core-excited state gradients are presented along the Jahn-Teller distorted geometry of the 1s -> pi* excited state. Our development may pave a new path to studying the dynamics of molecules in their core-excited states., QC 20210916

Published
2021
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9. Efficient implementation of isotropic cubic response functions for two-photon absorption cross sections within the self-consistent field approximation

Author

Ahmadzadeh, Karan, Scott, Mikael, Brand, Manuel, Vahtras, Olav, Li, Xin, Rinkevicius, Zilvinas, Norman, Patrick, Ahmadzadeh, Karan, Scott, Mikael, Brand, Manuel, Vahtras, Olav, Li, Xin, Rinkevicius, Zilvinas, and Norman, Patrick

Abstract

Within the self-consistent field approximation, computationally tractable expressions for the isotropic second-order hyperpolarizability have been derived and implemented for the calculation of two-photon absorption cross sections. The novel tensor average formulation presented in this work allows for the evaluation of isotropic damped cubic response functions using only similar to 3.3% (one-photon off-resonance regions) and similar to 10% (one-photon resonance regions) of the number of auxiliary Fock matrices required when explicitly calculating all the needed individual tensor components. Numerical examples of the two-photon absorption cross section in the one-photon off-resonance and resonance regions are provided for alanine-tryptophan and 2,5-dibromo-1,4-bis(2-(4-diphenylaminophenyl)vinyl)-benzene. Furthermore, a benchmark set of 22 additional small- and medium-sized organic molecules is considered. In all these calculations, a quantitative assessment is made of the reduced and approximate forms of the cubic response function in the one-photon off-resonance regions and results demonstrate a relative error of less than similar to 5% when using the reduced expression as compared to the full form of the isotropic cubic response function., QC 20210215

Published
2021
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14. Dalton Project: A Python platform for molecular- and electronic-structure simulations of complex systems

Author

Olsen, Jógvan Magnus Haugaard, primary, Reine, Simen, additional, Vahtras, Olav, additional, Kjellgren, Erik, additional, Reinholdt, Peter, additional, Hjorth Dundas, Karen Oda, additional, Li, Xin, additional, Cukras, Janusz, additional, Ringholm, Magnus, additional, Hedegård, Erik D., additional, Di Remigio, Roberto, additional, List, Nanna H., additional, Faber, Rasmus, additional, Cabral Tenorio, Bruno Nunes, additional, Bast, Radovan, additional, Pedersen, Thomas Bondo, additional, Rinkevicius, Zilvinas, additional, Sauer, Stephan P. A., additional, Mikkelsen, Kurt V., additional, Kongsted, Jacob, additional, Coriani, Sonia, additional, Ruud, Kenneth, additional, Helgaker, Trygve, additional, Jensen, Hans Jørgen Aa., additional, and Norman, Patrick, additional

Published
2020
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15. Dalton Project : A Python platform for molecular- and electronic-structure simulations of complex systems

Author

Olsen, Jogvan Magnus Haugaard, Reine, Simen, Vahtras, Olav, Kjellgren, Erik, Reinholdt, Peter, Dundas, Karen Oda Hjorth, Li, Xin, Cukras, Janusz, Ringholm, Magnus, Hedegard, Erik D., Di Remigio, Roberto, List, Nanna H., Faber, Rasmus, Tenorio, Bruno Nunes Cabral, Bast, Radovan, Pedersen, Thomas Bondo, Rinkevicius, Zilvinas, Sauer, Stephan P. A., Mikkelsen, Kurt V., Kongsted, Jacob, Coriani, Sonia, Ruud, Kenneth, Helgaker, Trygve, Jensen, Hans Jorgen Aa., Norman, Patrick, Olsen, Jogvan Magnus Haugaard, Reine, Simen, Vahtras, Olav, Kjellgren, Erik, Reinholdt, Peter, Dundas, Karen Oda Hjorth, Li, Xin, Cukras, Janusz, Ringholm, Magnus, Hedegard, Erik D., Di Remigio, Roberto, List, Nanna H., Faber, Rasmus, Tenorio, Bruno Nunes Cabral, Bast, Radovan, Pedersen, Thomas Bondo, Rinkevicius, Zilvinas, Sauer, Stephan P. A., Mikkelsen, Kurt V., Kongsted, Jacob, Coriani, Sonia, Ruud, Kenneth, Helgaker, Trygve, Jensen, Hans Jorgen Aa., and Norman, Patrick

Abstract

The Dalton Project provides a uniform platform access to the underlying full-fledged quantum chemistry codes Dalton and LSDalton as well as the PyFraME package for automatized fragmentation and parameterization of complex molecular environments. The platform is written in Python and defines a means for library communication and interaction. Intermediate data such as integrals are exposed to the platform and made accessible to the user in the form of NumPy arrays, and the resulting data are extracted, analyzed, and visualized. Complex computational protocols that may, for instance, arise due to a need for environment fragmentation and configuration-space sampling of biochemical systems are readily assisted by the platform. The platform is designed to host additional software libraries and will serve as a hub for future modular software development efforts in the distributed Dalton community., QC 20200702

Published
2020
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16. Nuclear dynamics in resonant inelastic X-ray scattering and X-ray absorption of methanol

Author

Vaz da Cruz, Vinícius, primary, Ignatova, Nina, additional, Couto, Rafael C., additional, Fedotov, Daniil A., additional, Rehn, Dirk R., additional, Savchenko, Viktoriia, additional, Norman, Patrick, additional, Ågren, Hans, additional, Polyutov, Sergey, additional, Niskanen, Johannes, additional, Eckert, Sebastian, additional, Jay, Raphael M., additional, Fondell, Mattis, additional, Schmitt, Thorsten, additional, Pietzsch, Annette, additional, Föhlisch, Alexander, additional, Gel’mukhanov, Faris, additional, Odelius, Michael, additional, and Kimberg, Victor, additional

Published
2019
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