Blar i NTNU Open på forfatter "Koch, Henrik"
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A Study of Thymine to Support Experimentalists - Interaction Energies and Core Ionisation Energies
Falck, Merete (Master thesis, 2016)This thesis aims at investigating the interaction energies between two thymine molecules at different geometries, discussing select wave function based approaches for finding interaction energies, and looking closer at the ... -
A theoretical and experimental benchmark study of core-excited states in nitrogen
Heilemann Myhre, Rolf; Wolf, Thomas J.A.; Cheng, Lan; Nandi, Saikat; Coriani, Sonia; Gühr, Marcus; Koch, Henrik (Journal article; Peer reviewed, 2018)The high resolution near edge X-ray absorption fine structure spectrum of nitrogen displays the vibrational structure of the core-excited states. This makes nitrogen well suited for assessing the accuracy of different ... -
An analysis of the performance of coupled cluster methods for K-edge core excitations and ionizations using standard basis sets
Carbone, Johanna P; Cheng, Lan; Myhre, Rolf Heilemann; Matthews, Devin A; Koch, Henrik; Coriani, Sonia (Journal article; Peer reviewed, 2019)An extensive analysis has been carried out of the performance of standard families of basis sets with the hierarchy of coupled cluster methods CC2, CCSD, CC3, and CCSDT in computing selected Oxygen, Carbon, and Nitrogen ... -
An efficient algorithm for Cholesky decomposition of electron repulsion integrals
Folkestad, Sarai Dery; Kjønstad, Eirik Fadum; Koch, Henrik (Journal article; Peer reviewed, 2019)Approximating the electron repulsion integrals using inner projections is a well-established approach to reduce the computational demands of electronic structure calculations. Here, we present a two-step Cholesky decomposition ... -
An Orbital Invariant Similarity Constrained CC2 Model
Stoll, Leo (Master thesis, 2024)Med inspirasjon fra similarity constrained coupled cluster singles and doubles (SCCSD) modellen utviklet av Kjønstad og Koch blir nødvendige likninger for utviklingen av en similarity constrained coupled cluster modell på ... -
An Orbital Invariant Similarity Constrained Coupled Cluster Model
Kjønstad, Eirik Fadum; Koch, Henrik (Journal article; Peer reviewed, 2019)We present a similarity constrained coupled cluster method able to describe conical intersections between two excited electronic states of the same symmetry. For a given pair of states, this singles and doubles method ... -
Asynchronous and Infinite Replica Exchange Transition Interface Sampling
Zhang, Daniel Tianhou (Doctoral theses at NTNU;2024:215, Doctoral thesis, 2024)A possible alternative to running chemical experiments in the laboratory could be to conduct them digitally instead, by running computer simulations. One prominent simulation technique is Molecular Dynamics (MD), which ... -
Calculation of Transition Moments Using the Extended Coupled Cluster Model ECC2
Skjelbred, Kristin Marie (Master thesis, 2014)As a part of the ongoing development of the multi level coupled cluster (MLCC) model ECC2, the work presented here is focused on obtaining transition moments associated with certain excitation energies. The ECC2 model ... -
Correlated natural transition orbitals for core excitation energies in multilevel coupled cluster models
Høyvik, Ida-Marie; Heilemann Myhre, Rolf; Koch, Henrik (Journal article; Peer reviewed, 2017)In this article, we present a black-box approach for the selection of orbital spaces when computing core excitation energies in the multilevel coupled cluster (MLCC) framework. Information available from the lower level ... -
Coupled cluster investigations of spectroscopic properties in molecular and crystalline systems
Hutcheson, Anders (Doctoral theses at NTNU;2022:343, Doctoral thesis, 2022)Theoretical studies of spectroscopic properties are of great value, both by themselves and in combination with experiments. The highly accurate coupled cluster methods are attractive options for such studies. Due to their ... -
Coupled cluster methods for nonadiabatic molecular dynamics
Kjønstad, Eirik F. (Doctoral theses at NTNU;2020:241, Doctoral thesis, 2020)Reliably predicting nuclear dynamics in excited electronic states requires an accurate representation of the involved electronic states. One challenge in this respect is the correct description of electronic degeneracies, ... -
Coupled cluster theory and strong light-matter coupling
Haugland, Tor Strømsem (Doctoral theses at NTNU;2023:354, Doctoral thesis, 2023)Chemical properties and reactivity are influenced by many external factors, such as temperature, pressure, solvents, and electric fields. In spectroscopy, molecules are probed using light, which yields information about ... -
Coupled Cluster Theory for Molecular Polaritons: Changing Ground and Excited States
Koch, Henrik; Tor S., Haugland; Eirik F., Kjønstad; Enrico, Ronca; Angel, Rubio (Peer reviewed; Journal article, 2020)We present an ab initio correlated approach to study molecules that interact strongly with quantum fields in an optical cavity. Quantum electrodynamics coupled cluster theory provides a nonperturbative description of ... -
Coupled-Cluster Equation of Motion method (QED-CCSD-1) for Triplet Excitations in Optical Cavities
Smedsrud, Wanjing Huang (Master thesis, 2024)Triplet elektronisk coupled-cluster singles-and-doubles (CCSD) metode med Equation of Motion (EOM) ekspanderes til optiske hull med ett-foton-approksimasjon som triplet EOM QED-CCSD-1 i denne masteroppgaven. Utledningen ... -
Crossing conditions in coupled cluster theory
Kjønstad, Eirik Fadum; Heilemann Myhre, Rolf; Martinez, Todd J.; Koch, Henrik (Journal article; Peer reviewed, 2017)We derive the crossing conditions at conical intersections between electronic states in coupled cluster theory and show that if the coupled cluster Jacobian matrix is nondefective, two (three) independent conditions are ... -
Density-Based Formulation of Multi-Level Hartree-Fock Theory
Dundas, Karen Oda Hjorth (Master thesis, 2016)A scheme for multi-level (embedded) Hartree-Fock theory is developed. The goal is to reduce computational costs by treating different parts of an electronic system with different degrees of accuracy. In this thesis, a ... -
Describing ground and excited state potential energy surfaces for molecular photoswitches using coupled cluster models
Hutcheson, Anders; Paul, Alexander Christian; Myhre, Rolf Heilemann; Koch, Henrik; Høyvik, Ida-Marie (Peer reviewed; Journal article, 2021)n this article, we use two extensively studied systems, a retinal model system and azobenzene, to explore the use of coupled cluster models for describing ground and singlet excited state potential energy surfaces of ... -
Development and implementation of extended CC2 models
Heilemann Myhre, Rolf (Master thesis, 2013)This thesis is part of an ongoing research project into the development and implementation of multi-level coupled cluster (MLCC) theory. In MLCC, the orbital space is divided into two or more subspaces. Based on which ... -
Efficient algorithms for coupled cluster with approximate triples for larger molecular systems
Paul, Alexander C. (Doctoral theses at NTNU;2021:339, Doctoral thesis, 2021)Spectroscopic techniques are widely used to study matter in a non-invasive manner. With increasing complexity of the experiments conducted, theoretical simulations become more important to gain additional insight into the ... -
Energy-Based Molecular Orbital Localization in a Specific Spatial Region
Giovannini, Tommaso; Koch, Henrik (Peer reviewed; Journal article, 2020)We present a novel energy-based localization procedure able to localize molecular orbitals into predefined spatial regions. The method is defined in a multiscale framework based on the multilevel Hartree–Fock approach. In ...