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 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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
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 ... -
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 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 ... -
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 ... -
Optical rotation from coupled cluster and density functional theories
Haghdani, Shokouh (Doctoral theses at NTNU; 2018:31, Doctoral thesis, 2018)Chiral compounds are of fundamental importance in medical chemistry, biochemistry, and industry. Optical rotation, which is one of the most well-known optical responses of chiral molecules to an electromagnetic field, is ...