Author
Kasper Hald
Other affiliations: Aarhus University
Bio: Kasper Hald is an academic researcher from Danske Bank. The author has contributed to research in topics: Coupled cluster & Triplet state. The author has an hindex of 14, co-authored 21 publications receiving 2524 citations. Previous affiliations of Kasper Hald include Aarhus University.
Topics: Coupled cluster, Triplet state, Excited state, Singlet state, Excitation
Papers
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Vilnius University1, University of Ferrara2, Aarhus University3, University of Oslo4, Royal Institute of Technology5, Electromagnetic Geoservices6, University of Trieste7, Norwegian Computing Center8, University of Southern Denmark9, University of Santiago de Compostela10, Danske Bank11, Ruhr University Bochum12, Norwegian Meteorological Institute13, Norwegian Defence Research Establishment14, University of Auckland15, Norwegian University of Science and Technology16, Information Technology University17, Technical University of Ostrava18, Linköping University19, Karlsruhe Institute of Technology20, ETH Zurich21, Australian National University22, University of Modena and Reggio Emilia23, Cisco Systems, Inc.24, University of Buenos Aires25, University of Copenhagen26, University of Erlangen-Nuremberg27, Kazimierz Wielki University in Bydgoszcz28, National Scientific and Technical Research Council29, University of Valencia30, Paul Sabatier University31, University of Melbourne32, University of Nottingham33, University of Bristol34, CLC bio35, Princeton University36, La Trobe University37, Clemson University38
TL;DR: Dalton is a powerful general‐purpose program system for the study of molecular electronic structure at the Hartree–Fock, Kohn–Sham, multiconfigurational self‐consistent‐field, Møller–Plesset, configuration‐interaction, and coupled‐cluster levels of theory.
Abstract: Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, confi ...
1,212 citations
TL;DR: In this paper, the triplet and triplet vertical excitation energies of trans-azobenzene were investigated using an explicitly spin coupled basis and the resolution of the identity approximation for two-electron integrals.
Abstract: Triplet excitation energies within the approximate coupled cluster singles and doubles model CC2 have been implemented using an explicitly spin coupled basis and the resolution of the identity approximation for two-electron integrals. This approach reduces substantially the requirements for CPU time, disk space and memory, and extends the applicability of CC2 for triplet excited states to molecules that could not be studied before with this method. We report an application to the lowest singlet and triplet vertical excitation energies of trans-azobenzene. An accurate ab initio geometry optimized at the MP2/cc-pVTZ level is presented, and CC2 calculations in the aug-cc-pVTZ basis set with 874 basis functions are combined with coupled cluster singles and doubles (CCSD) calculations in modest basis sets to obtain the best possible estimates for the vertical excitation energies. The results show that recently reported SOPPA calculations are unreliable.
Good agreement with experiment is obtained for the lowest excited singlet state S1, but for the lowest triplet state T1 the results indicate a large difference between the vertical excitation energy and the experimentally observed transition.
122 citations
TL;DR: In this paper, triplet and singlet excitation energies have been calculated for Ne, H2O, HF, BH, N2 and C2 using the full configuration interaction (FCI) model and the coupled-cluster model hierarchy CCS, CC2, CCSD, CC3, CC4, CC5, CC6, CC7, CC8 and CCSDT.
Abstract: Triplet excitation energies have been calculated for Ne, H2O, HF, BH, N2, and C2 using the full configuration interaction (FCI) model and the coupled-cluster model hierarchy CCS, CC2, CCSD, CC3, and CCSDT, where CCS, CCSD, and CCSDT are the standard coupled-cluster models where singles, doubles and triples are successively added and where CC2 and CC3 are approximations to the CCSD and CCSDT models where approximations are introduced in the highest amplitude equations. Comparing the coupled-cluster excitation energies with the FCI results shows that the excitation energies are improved at each level in the hierarchy up to CC3. The CC3 and CCSDT excitation energies have similar accuracy for the single excitation dominated excitation energies, whereas the double excitation dominated excitation energies are significantly improved also from CC3 to CCSDT. Singlet excitation energies have also been calculated for HF using the coupled-cluster hierarchy up to CCSDT. Triplet and singlet excitation energies with sim...
77 citations
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TL;DR: In this article, the essential aspects of coupled-cluster theory are explained and illustrated with informative numerical results, showing that the theory offers the most accurate results among the practical ab initio electronic-structure theories applicable to moderate-sized molecules.
Abstract: Today, coupled-cluster theory offers the most accurate results among the practical ab initio electronic-structure theories applicable to moderate-sized molecules. Though it was originally proposed for problems in physics, it has seen its greatest development in chemistry, enabling an extensive range of applications to molecular structure, excited states, properties, and all kinds of spectroscopy. In this review, the essential aspects of the theory are explained and illustrated with informative numerical results.
2,667 citations
Vilnius University1, University of Ferrara2, Aarhus University3, University of Oslo4, Royal Institute of Technology5, Electromagnetic Geoservices6, University of Trieste7, Norwegian Computing Center8, University of Southern Denmark9, University of Santiago de Compostela10, Danske Bank11, Ruhr University Bochum12, Norwegian Meteorological Institute13, Norwegian Defence Research Establishment14, University of Auckland15, Norwegian University of Science and Technology16, Information Technology University17, Technical University of Ostrava18, Linköping University19, Karlsruhe Institute of Technology20, ETH Zurich21, Australian National University22, University of Modena and Reggio Emilia23, Cisco Systems, Inc.24, University of Buenos Aires25, University of Copenhagen26, University of Erlangen-Nuremberg27, Kazimierz Wielki University in Bydgoszcz28, National Scientific and Technical Research Council29, University of Valencia30, Paul Sabatier University31, University of Melbourne32, University of Nottingham33, University of Bristol34, CLC bio35, Princeton University36, La Trobe University37, Clemson University38
TL;DR: Dalton is a powerful general‐purpose program system for the study of molecular electronic structure at the Hartree–Fock, Kohn–Sham, multiconfigurational self‐consistent‐field, Møller–Plesset, configuration‐interaction, and coupled‐cluster levels of theory.
Abstract: Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, confi ...
1,212 citations
TL;DR: In this article, a set of 28 medium-sized organic molecules is assembled that cover the most important classes of chromophores including polyenes and other unsaturated aliphatic compounds, aromatic hydrocarbons, heterocycles, carbonyl compounds, and nucleobases.
Abstract: A benchmark set of 28 medium-sized organic molecules is assembled that covers the most important classes of chromophores including polyenes and other unsaturated aliphatic compounds, aromatic hydrocarbons, heterocycles, carbonyl compounds, and nucleobases. Vertical excitation energies and one-electron properties are computed for the valence excited states of these molecules using both multiconfigurational second-order perturbation theory, CASPT2, and a hierarchy of coupled cluster methods, CC2, CCSD, and CC3. The calculations are done at identical geometries (MP26-31G*) and with the same basis set (TZVP). In most cases, the CC3 results are very close to the CASPT2 results, whereas there are larger deviations with CC2 and CCSD, especially in singlet excited states that are not dominated by single excitations. Statistical evaluations of the calculated vertical excitation energies for 223 states are presented and discussed in order to assess the relative merits of the applied methods. CC2 reproduces the CC3 reference data for the singlets better than CCSD. On the basis of the current computational results and an extensive survey of the literature, we propose best estimates for the energies of 104 singlet and 63 triplet excited states.
860 citations
TL;DR: This review provides a guide to established EOM methods illustrated by examples that demonstrate the types of target states currently accessible by EOM, and touches on some formal aspects of the theory and important current developments.
Abstract: The equation-of-motion coupled-cluster (EOM-CC) approach is a versatile electronic-structure tool that allows one to describe a variety of multiconfigurational wave functions within single-reference formalism. This review provides a guide to established EOM methods illustrated by examples that demonstrate the types of target states currently accessible by EOM. It focuses on applications of EOM-CC to electronically excited and open-shell species. The examples emphasize EOM's advantages for selected situations often perceived as multireference cases [e.g., interacting states of different nature, Jahn-Teller (JT) and pseudo-JT states, dense manifolds of ionized states, diradicals, and triradicals]. I also discuss limitations and caveats and offer practical solutions to some problematic situations. The review also touches on some formal aspects of the theory and important current developments.
856 citations
TL;DR: Near-infrared-emissive polymer-carbon nanodots possess two-photon fluorescence; in vivo bioimaging and red-light-emitting diodes based on these PCNDs are demonstrated.
Abstract: Near-infrared-emissive polymer-carbon nanodots (PCNDs) are fabricated by a newly developed facile, high-output strategy. The PCNDs emit at a wavelength of 710 nm with a quantum yield of 26.28%, which is promising for deep biological imaging and luminescent devices. Moreover, the PCNDs possess two-photon fluorescence; in vivo bioimaging and red-light-emitting diodes based on these PCNDs are demonstrated.
620 citations