0000000000526122

AUTHOR

Heiko Appel

showing 3 related works from this author

Ab initio angle- and energy-resolved photoelectron spectroscopy with time-dependent density-functional theory

2012

We present a time-dependent density-functional method able to describe the photoelectron spectrum of atoms and molecules when excited by laser pulses. This computationally feasible scheme is based on a geometrical partitioning that efficiently gives access to photoelectron spectroscopy in time-dependent density-functional calculations. By using a geometrical approach, we provide a simple description of momentum-resolved photoemission including multiphoton effects. The approach is validated by comparison with results in the literature and exact calculations. Furthermore, we present numerical photoelectron angular distributions for randomly oriented nitrogen molecules in a short near-infrared…

Atomic Physics (physics.atom-ph)Photoemission spectroscopyAb initioFOS: Physical sciences02 engineering and technology01 natural sciences7. Clean energySpectral lineSettore FIS/03 - Fisica Della MateriaPhysics - Atomic PhysicsX-ray photoelectron spectroscopyTDDFTABOVE-THRESHOLD IONIZATION; LASER FIELDS; WAVE-FUNCTIONS; PHOTOEMISSION; CLUSTERS; SYSTEMS; PULSESMesoscale and Nanoscale Physics (cond-mat.mes-hall)0103 physical sciencesPhysics::Atomic and Molecular ClustersPhysics - Atomic and Molecular ClustersPhysics::Atomic Physics010306 general physicsPhysicsCondensed Matter - Mesoscale and Nanoscale PhysicsAtoms in moleculesTime-dependent density functional theory021001 nanoscience & nanotechnologyAtomic and Molecular Physics and Optics3. Good healthStrong field ionizationExcited stateDensity functional theoryAtomic physicsAtomic and Molecular Clusters (physics.atm-clus)0210 nano-technology
researchProduct

Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems

2020

Over the last few years, extraordinary advances in experimental and theoretical tools have allowed us to monitor and control matter at short time and atomic scales with a high degree of precision. An appealing and challenging route toward engineering materials with tailored properties is to find ways to design or selectively manipulate materials, especially at the quantum level. To this end, having a state-of-the-art ab initio computer simulation tool that enables a reliable and accurate simulation of light-induced changes in the physical and chemical properties of complex systems is of utmost importance. The first principles real-space-based Octopus project was born with that idea in mind,…

spectroscopyPhotonelectronic-structure calculationsComputer sciencespectraQuantum dynamicsmolecular-dynamicsComplex systemGeneral Physics and AstronomyFOS: Physical sciences010402 general chemistryspin01 natural sciencesSettore FIS/03 - Fisica Della MateriaEngineeringTDDFTreal-space0103 physical sciencesoctopusgeneralized gradient approximationPhysical and Theoretical Chemistrydensity-functional theoryMassively parallelQuantumChemical Physicsreal time010304 chemical physicsComputational Physics (physics.comp-ph)scientific software0104 chemical sciencestotal-energy calculationsphysics.comp-phPhysical SciencesChemical Sciencespolarizable continuum modelState of matterSystems engineeringLight drivenDensity functional theoryPhysics - Computational Physics
researchProduct

Many-body Green's function theory for electron-phonon interactions: ground state properties of the Holstein dimer

2015

We study ground-state properties of a two-site, two-electron Holstein model describing two molecules coupled indirectly via electron-phonon interaction by using both exact diagonalization and self-consistent diagrammatic many-body perturbation theory. The Hartree and self-consistent Born approximations used in the present work are studied at different levels of self-consistency. The governing equations are shown to exhibit multiple solutions when the electron-phonon interaction is sufficiently strong whereas at smaller interactions only a single solution is found. The additional solutions at larger electron-phonon couplings correspond to symmetry-broken states with inhomogeneous electron de…

ground state propertiesGeneral Physics and AstronomyFOS: Physical sciences02 engineering and technology53001 natural sciencesCondensed Matter - Strongly Correlated Electronssymbols.namesakeQuantum mechanics0103 physical sciencesSymmetry breakingPhysical and Theoretical ChemistryBorn approximationPerturbation theory010306 general physicsPhysicsBipolaronta114Strongly Correlated Electrons (cond-mat.str-el)many-body perturbation theoryHartree540021001 nanoscience & nanotechnologySymmetry (physics)3. Good healthGreen's functionelectron-phonon interactionsymbols0210 nano-technologyGround state
researchProduct