Analytical Nuclear Excited-State Gradients for the Second-Order Approximate Coupled-Cluster Singles and Doubles (CC2) Method Employing Uncoupled Frozen-Density Embedding

AbstractThe dipole-bound excited state of the methylene nitrile anion (CH2CN−) has been suggested as a candidate carrier for a diffuse interstellar band (DIB) at 803.8 nm. Its corresponding radical has been detected in the interstellar medium (ISM), making the existence for the anion possible. This work applies state-of-the-art ab initio methods such as coupled cluster theory to reproduce accurately the electronic excitations for CH2CN− and the similar methylene enolate anion, CH2CHO−. This same approach has been employed to indicate that 19 other anions may possess electronically excited states, five of which are valence in nature. Concurrently, in order to assist in the detection of these anions in the ISM, work has also been directed towards predicting vibrational frequencies and spectroscopic constants for these anions through the use of quartic force fields (QFFs). Theoretical rovibrational work on anions has thus far included studies of CH2CN−, C3H−, and is currently ongoing for similar systems.

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The extended explicitly-correlated second-order approximate coupled-cluster singles and doubles ansatz suitable for response theory

The Journal of Chemical Physics ◽

10.1063/1.5094434 ◽

2019 ◽

Vol 150 (18) ◽

pp. 184110 ◽

Cited By ~ 1

Author(s):

Sebastian Höfener ◽

Nils Schieschke ◽

Wim Klopper ◽

Andreas Köhn

Keyword(s):

Second Order ◽

Coupled Cluster ◽

Response Theory ◽

Explicitly Correlated

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Tensor Hypercontraction Equation-of-Motion Second-Order Approximate Coupled Cluster: Electronic Excitation Energies in O(N4) Time

The Journal of Physical Chemistry B ◽

10.1021/jp4021905 ◽

2013 ◽

Vol 117 (42) ◽

pp. 12972-12978 ◽

Cited By ~ 41

Author(s):

Edward G. Hohenstein ◽

Sara I. L. Kokkila ◽

Robert M. Parrish ◽

Todd J. Martínez

Keyword(s):

Electronic Excitation ◽

Equation Of Motion ◽

Second Order ◽

Coupled Cluster ◽

Excitation Energies

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Improved convergence of Hartree–Fock style excited-state wavefunctions using second-order optimisation with an exact Hessian

Theoretical Chemistry Accounts ◽

10.1007/s00214-013-1400-6 ◽

2013 ◽

Vol 132 (11) ◽

Cited By ~ 3

Author(s):

Gareth W. Richings ◽

Peter B. Karadakov

Keyword(s):

Excited State ◽

Second Order ◽

Hartree Fock ◽

State Wavefunctions

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Assessing the Accuracy of Simplified Coupled Cluster Methods for Electronic Excited States in F0 Actinide Compounds

10.26434/chemrxiv.8396855 ◽

2019 ◽

Author(s):

Artur Nowak ◽

Paweł Tecmer ◽

Katharina Boguslawski

Keyword(s):

Electron Transfer ◽

Excited State ◽

Excited States ◽

Coupled Cluster ◽

Electronic Excitations ◽

Electronic Excited States ◽

Benchmark Study ◽

Double Electron ◽

Different Types ◽

Cluster Methods

<p>We present a benchmark study of the performance of various recently presented EOM-pCCD-based methods to model ground and excited state properties of a set of f0 actinide species that feature different types of electronic excitations, like local excitations or charge transfer. Our data suggests that the recently developed EOM-pCCD-LCCSD method outperforms conventional approaches like EOM-CCSD reducing the standard error by a factor of 2 (to 0.25 eV). Thus, EOM-pCCD-LCCSD can be considered as an alternative to model excited states in challenging systems, especially those who feature a double electron transfer for which EOM-CCSD typically fails.</p>

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Visible-light Photoresponse of Nitrogen-doped TiO2: Excited State Studies Using Time-dependent Density Functional Theory and Equation-of-Motion Coupled Cluster Methods

MRS Proceedings ◽

10.1557/proc-1263-y04-06 ◽

2010 ◽

Vol 1263 ◽

Author(s):

Niranjan Govind ◽

Roger Rousseau ◽

Amity Andersen ◽

Karol Kowalski

Keyword(s):

Excited State ◽

Density Functional ◽

Equation Of Motion ◽

Coupled Cluster ◽

Functional Theory ◽

Experimental Findings ◽

High Level ◽

Cluster Methods ◽

Compare And Contrast

AbstractTo shed light on the nature of the electronic states at play in N-doped TiO2 nanoparticles, we have performed detailed ground and excited state calculations on pure and N-doped TiO2 rutile using an embedding model. We have validated our model by comparing ground-state embedded results with those obtained from periodic DFT calculations. Our results are consistent with periodic calculations. Using this embedding model we have performed B3LYP based TDDFT calculations of the excited state spectrum. We have also studied the lowest excitations using high-level equation-of-motion coupled cluster (EOMCC) approaches involving all single and inter-band double excitations. We compare and contrast the nature of the excitations in detail for the pure and doped systems using these calculations. Our calculations indicate a lowering of the bandgap and confirm the role of the N3- states on the UV/Vis spectrum of N-doped TiO2 rutile supported by experimental findings.

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