Browsing NTNU Open by Author "Koch, Henrik"
Now showing items 21-40 of 57
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Engineering chemistry in the strong coupling regime: theoretical insights and new perspectives
Riso, Rosario Roberto (Doctoral theses at NTNU;2023:316, Doctoral thesis, 2023)Cavity quantum optics deals with the interaction of photons and molecules inside an optical cavity, i.e., in the region between two closely spaced mirrors. Perfect optical cavities can only support certain frequencies of ... -
Equation-of-motion coupled-cluster method with double electron-attaching operators: Theory, implementation, and benchmarks
Gulania, Sahil; Kjønstad, Eirik Fadum; Stanton, John F.; Koch, Henrik; Krylov, Anna I. (Journal article, 2021)We report a production-level implementation of the equation-of-motion (EOM) coupled-cluster (CC) method with double electron-attaching (DEA) EOM operators of 2p and 3p1h types, EOM-DEA-CCSD. This ansatz, suitable for ... -
Excited State Absorption of Uracil in the Gas Phase: Mapping the Main Decay Paths by Different Electronic Structure Methods
Fedotov, Daniil; Paul, Alexander Christian; Posocco, Paolo; Santoro, Fabrizio; Garavelli, Marco; Koch, Henrik; Coriani, Sonia; Improta, Roberto (Peer reviewed; Journal article, 2021)We present a computational study of the one-photon and excited-state absorption (ESA) from the two lowest energy excited states of uracil in the gas phase: an nπ* dark state (1n) and the lowest energy bright ππ* state (1π). ... -
An Extended CCSD Model Including Triple Excitations for Core-Ionization Energies
Bredvold, Kaja Louise Havig (Master thesis, 2018)A model for calculation of core-ionization energies is developed within the equations-of-motion coupled cluster framework with application of the CVS approximation. The model deviates from EOM-CCSD by inclusion of triple ... -
Ferroelectric Tungsten Bronzes
Olsen, Gerhard Henning (Doctoral thesis at NTNU;2016:237, Doctoral thesis, 2016)Ferroelectric materials are everywhere in the modern society, from consumer electronics to car engines. Applications cover a whole range of devices such as sensors, actuators and transducers due to their dielectric or ... -
Large-Scale Electron Correlation Calculations: Rank-Reduced Full Configuration Interaction
Fales, B Scott; Seritan, Stefan; Settje, Nick F; Levine, Benjamin G; Koch, Henrik; Martinez, Todd J. (Journal article, 2018)We present the rank-reduced full configuration interaction (RR-FCI) method, a variational approach for the calculation of extremely large full configuration interaction (FCI) wave functions. In this report, we show that ... -
Modeling Chemistry in QED Cavities using Coupled Cluster
Haugland, Tor Strømsem (Master thesis, 2019)I denne avhandlingen introduseres kvanteelektrodynamisk ''coupled cluster'' teori (QED-CC) som en ny og nøyaktig ab initio teori for å undersøke sterk kobling mellom lys og materie i optiske kaviteter. Ligningene for ... -
Modeling enviromental effects with coupled cluster and particle-breaking Hartree-Fock theory
Paul, Regina (Doctoral theses at NTNU;2024:159, Doctoral thesis, 2024)Chemical phenomena commonly occur within specific environments, such as solutions or surfaces. An emerging area, termed on-water catalysis, exemplifies this, where chemical reactions experience significant acceleration at ... -
Molecular dynamics simulation of sodium diffusion in amorphous carbon using optimized reactive force field
Nguyen, Anh Quynh (Master thesis, 2017)A reactive force fieldhas been optimized to study sodium intercalation and diffusion into graphitic carbon at high temperature. The resulting force field reproduces training data and calculates new data with moderate ... -
Molecular orbital theory in cavity QED environments
Riso, Rosario Roberto; Haugland, Tor S.; Ronca, Enrico; Koch, Henrik (Peer reviewed; Journal article, 2022)Coupling between molecules and vacuum photon fields inside an optical cavity has proven to be an effective way to engineer molecular properties, in particular reactivity. To ease the rationalization of cavity induced effects ... -
Multi-method atomistic modelling of sodium-carbon interactions: Atomistic modelling towards the increased durability of carbon cathodes in primary aluminium production
Hjertenæs, Eirik (Doctoral theses at NTNU;2017:9, Doctoral thesis, 2017)Karbonmaterialer brukes som kledning under produksjonen av primærmetall. Høy temperatur, strøm og et kjemisk tærende miljø sliter materialene under drift. En bidragende årsak til slitasjen er inntrengning av natrium. ... -
Multilevel CC2 and CCSD in Reduced Orbital Spaces: Electronic Excitations in Large Molecular Systems
Folkestad, Sarai Dery; Kjønstad, Eirik Fadum; Goletto, Linda; Koch, Henrik (Peer reviewed; Journal article, 2021)We present efficient implementations of the multilevel CC2 (MLCC2) and multilevel CCSD (MLCCSD) models. As the system size increases, MLCC2 and MLCCSD exhibit the scaling of the lower-level coupled cluster model. To treat ... -
Multilevel CC2 and CCSD Methods with Correlated Natural Transition Orbital
Folkestad, Sarai Dery; Koch, Henrik (Peer reviewed; Journal article, 2019)In the multilevel coupled cluster approach, an active orbital space is treated at a higher level of coupled cluster theory than the remaining inactive orbitals. We introduce the multilevel CC2 method where CC2 is used for ... -
Multilevel coupled cluster methods for large molecular systems
Folkestad, Sarai Dery (Doctoral theses at NTNU;2020:240, Doctoral thesis, 2020)The coupled cluster hierarchy of models can be used to accurately describe electronic excitations in molecular systems. However, the standard coupled cluster models are expensive and their cost severely limits the size of ... -
Multilevel coupled cluster theory: Development, implementation and application of multilevel coupled cluster theory for core and valence excited states
Myhre, Rolf Heilemann (Doctoral thesis at NTNU;2016:267, Doctoral thesis, 2016)This thesis consist of seven papers and an introduction describing the ongoing development and applications of multilevel coupled cluster theory. Coupled cluster theory is one of the most accurate, but also one of the ... -
Multiscale models for large molecular systems: from development to applications
Goletto, Linda (Doctoral theses at NTNU;2023:17, Doctoral thesis, 2023)The atomistic description of complex molecular systems, such as solutions and biological moieties, requires some sort of compromise between computational efforts and accuracy. Low-level models can treat thousands of atoms, ... -
A new and efficient implementation of CC3
Paul, Alexander Christian; Myhre, Rolf Heilemann; Koch, Henrik (Peer reviewed; Journal article, 2020)We present a new and efficient implementation of the closed shell coupled cluster singles and doubles with perturbative triples method (CC3) in the electronic structure program eT. Asymptotically, a ground state calculation ... -
A NEXAFS study of thymine tautomers using coupled cluster methods
Lid, Solrun (Master thesis, 2018)The gas phase geometries of the thirteen different tautomers of thymine were optimized at the level of coupled cluster singles, doubles and perturbative triples, CCSD(T), using an aug-cc-pVDZ basis set. The total energy ... -
Observation of Ultrafast Intersystem Crossing in Thymine by Extreme Ultraviolet Time-Resolved Photoelectron Spectroscopy
Wolf, Thomas J. A.; Parrish, Robert M; Myhre, Rolf Heilemann; Martinez, Todd J.; Koch, Henrik; Gühr, Marcus (Journal article; Peer reviewed, 2019)We studied the photoinduced ultrafast relaxation dynamics of the nucleobase thymine using gas-phase time-resolved photoelectron spectroscopy. By employing extreme ultraviolet pulses from high harmonic generation for ... -
On the characteristic features of ionization in QED environments
Riso, Rosario Roberto; Haugland, Tor S.; Ronca, Enrico; Koch, Henrik (Peer reviewed; Journal article, 2022)The ionization of molecular systems is important in many chemical processes, such as electron transfer and hot electron injection. Strong coupling between molecules and quantized fields (e.g., inside optical cavities) ...