Search Results - "Kjønstad, Eirik F."

Coupled Cluster Theory for Molecular Polaritons: Changing Ground and Excited States by Haugland, Tor S., Ronca, Enrico, Kjønstad, Eirik F., Rubio, Angel, Koch, Henrik

“…We present an ab initio correlated approach to study molecules that interact strongly with quantum fields in an optical cavity. Quantum electrodynamics coupled…”
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Coupled Cluster Theory for Nonadiabatic Dynamics: Nuclear Gradients and Nonadiabatic Couplings in Similarity Constrained Coupled Cluster Theory by Kjønstad, Eirik F, Angelico, Sara, Koch, Henrik

“…Coupled cluster theory is one of the most accurate electronic structure methods for predicting ground and excited state chemistry. However, the presence of…”
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Multilevel CC2 and CCSD in Reduced Orbital Spaces: Electronic Excitations in Large Molecular Systems by Folkestad, Sarai Dery, Kjønstad, Eirik F, Goletto, Linda, Koch, Henrik

“…We present efficient implementations of the multilevel CC2 (MLCC2) and multilevel CCSD (MLCCSD) models. As the system size increases, MLCC2 and MLCCSD exhibit…”
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Resolving the Notorious Case of Conical Intersections for Coupled Cluster Dynamics by Kjønstad, Eirik F, Koch, Henrik

“…The motion of electrons and nuclei in photochemical events often involves conical intersections, or degeneracies between electronic states. They serve as…”
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Analytical Evaluation of Ground State Gradients in Quantum Electrodynamics Coupled Cluster Theory by Lexander, Marcus T., Angelico, Sara, Kjønstad, Eirik F., Koch, Henrik

“…Analytical gradients of potential energy surfaces play a central role in quantum chemistry, allowing for molecular geometry optimizations and molecular…”
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An Orbital Invariant Similarity Constrained Coupled Cluster Model by Kjønstad, Eirik F, Koch, Henrik

“…We present a similarity constrained coupled cluster method able to describe conical intersections between two excited electronic states of the same symmetry…”
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Biorthonormal Formalism for Nonadiabatic Coupled Cluster Dynamics by Kjønstad, Eirik F, Koch, Henrik

“…In coupled cluster theory, the electronic states are biorthonormal in the sense that the left states are orthonormal to the right states. Here, we present an…”
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Linear-Scaling Implementation of Multilevel Hartree–Fock Theory by Goletto, Linda, Kjønstad, Eirik F, Folkestad, Sarai D, Høyvik, Ida-Marie, Koch, Henrik

“…We introduce a new algorithm for the construction of the two-electron contributions to the Fock matrix in multilevel Hartree–Fock (MLHF) theory. In MLHF, the…”
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A critical investigation of proposed electrostatic corrections to quantum mechanical volumes: the importance of variation and the irrelevance of imbalance by Kjønstad, Eirik F., Moxnes, John F., Jensen, Tomas L., Unneberg, Erik

“…The crystal density of neutral and ionic molecular crystals is remarkably well approximated by the enclosed volume of molecular surfaces, where these surfaces…”
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All molecular surfaces are equal: demanding invariance of predictions in linear single-variable models by Kjønstad, Eirik F., Moxnes, John F., Jensen, Tomas L., Unneberg, Erik

“…The molecular surface has been suggested to be a region of the molecule, where information of non-covalent intermolecular interactions is present. Many workers…”
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Understanding failures in electronic structure methods arising from the geometric phase effect by Kjønstad, Eirik F, Koch, Henrik

“…We show that intermediate normalization of the electronic wave function, where a constant component is enforced, will lead to an asymptotic discontinuity at…”
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Determining minimum energy conical intersections by enveloping the seam: exploring ground and excited state intersections in coupled cluster theory by Angelico, Sara, Kjønstad, Eirik F, Koch, Henrik

“…Minimum energy conical intersections can be used to rationalize photochemical processes. In this Letter, we examine an algorithm to locate these structures…”
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Non-adiabatic derivative coupling elements for the coupled cluster singles and doubles model by Kjønstad, Eirik F, Koch, Henrik

“…We present an efficient implementation of analytical non-adiabatic derivative coupling elements for the coupled cluster singles and doubles model. The…”
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Coupled cluster theory for nonadiabatic dynamics: nuclear gradients and nonadiabatic couplings in similarity constrained coupled cluster theory by Kjønstad, Eirik F, Angelico, Sara, Koch, Henrik

“…Coupled cluster theory is one of the most accurate electronic structure methods for predicting ground and excited state chemistry. However, the presence of…”
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Generalized coupled cluster theory for ground and excited state intersections by Rossi, Federico, Kjønstad, Eirik F, Angelico, Sara, Koch, Henrik

“…Coupled cluster theory in the standard formulation is unable to correctly describe conical intersections among states of the same symmetry. This limitation has…”
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A biorthonormal formalism for nonadiabatic coupled cluster dynamics by Kjønstad, Eirik F, Koch, Henrik

“…In coupled cluster methods, the electronic states are biorthonormal in the sense that the left states are orthonormal to the right states. Here we present an…”
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Fermionic tensor network contraction for arbitrary geometries by Gao, Yang, Zhai, Huanchen, Gray, Johnnie, Peng, Ruojing, Park, Gunhee, Liu, Wen-Yuan, Kjønstad, Eirik F, Chan, Garnet Kin-Lic

“…We describe our implementation of fermionic tensor network contraction on arbitrary lattices within both a globally ordered and locally ordered formalism. We…”
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Resolving the notorious case of conical intersections for coupled cluster dynamics by Kjønstad, Eirik F, Koch, Henrik

“…The motion of electrons and nuclei in photochemical events often involve conical intersections, degeneracies between electronic states. They serve as funnels…”
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Unexpected hydrogen dissociation in thymine: predictions from a novel coupled cluster theory by Kjønstad, Eirik F, Fajen, O. Jonathan, Paul, Alexander C, Angelico, Sara, Mayer, Dennis, Gühr, Markus, Wolf, Thomas J. A, Martínez, Todd J, Koch, Henrik

“…The fate of thymine upon excitation by ultraviolet radiation has been the subject of intense debate over the past three decades. Today, it is widely believed…”
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Accelerated multimodel Newton-type algorithms for faster convergence of ground and excited state coupled cluster equations by Kjønstad, Eirik F, Folkestad, Sarai D, Koch, Henrik

“…We introduce a multimodel approach to solve coupled cluster equations, employing a quasi Newton algorithm for the ground state and an Olsen algorithm for the…”
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