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

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>

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

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>

scholarly journals Theoretical Electronic and Rovibrational Studies for Anions of Interest to the DIBs

2013 ◽  
Vol 9 (S297) ◽  
pp. 344-348 ◽  
Author(s):  
R. C. Fortenberry
Keyword(s):  
Excited State ◽  
Excited States ◽  
State Of The Art ◽  
Spectroscopic Constants ◽  
Coupled Cluster ◽  
Electronic Excitations ◽  
Electronically Excited States ◽  
Coupled Cluster Theory ◽  
Electronically Excited ◽  
Enolate Anion

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.

Carbon monoxide activation by atomic thorium: ground and excited state reaction pathways

2019 ◽  
Vol 21 (44) ◽  
pp. 24469-24477
Author(s):  
Isuru R. Ariyarathna ◽  
Evangelos Miliordos
Keyword(s):  
Carbon Monoxide ◽  
Excited State ◽  
Potential Energy ◽  
Excited States ◽  
Configuration Interaction ◽  
Reaction Pathways ◽  
Coupled Cluster ◽  
Energy Profiles ◽  
Cluster Methods ◽  
Potential Energy Profiles

Ground and excited states of ThCO and OThC isomers are studied with multi-reference configuration interaction and coupled cluster methods. The potential energy profiles connecting the states of the two nearly isoenergetic molecules are constructed.

scholarly journals Assessing the accuracy of simplified coupled cluster methods for electronic excited states in f0 actinide compounds

2019 ◽  
Vol 21 (35) ◽  
pp. 19039-19053
Author(s):  
Artur Nowak ◽  
Paweł Tecmer ◽  
Katharina Boguslawski
Keyword(s):  
Excited States ◽  
Potential Energy Surfaces ◽  
Electronic Excitation ◽  
Closed Shell ◽  
Coupled Cluster ◽  
Excitation Energies ◽  
Electronic Excited States ◽  
State Potential ◽  
Energy Surfaces ◽  
Cluster Methods

We scrutinize the performance of different variants of equation of motion coupled cluster (EOM-CC) methods to predict electronic excitation energies and excited state potential energy surfaces in closed-shell actinide species.

scholarly journals Structure of Low-Lying Excited States of Guanine in DNA and Solution: Combined Molecular Mechanics and High-Level Coupled Cluster Studies

2007 ◽  
Vol 2007 ◽  
pp. 1-5 ◽  
Author(s):  
Karol Kowalski ◽  
Marat Valiev
Keyword(s):  
Excited State ◽  
Excitation Energy ◽  
Molecular Mechanics ◽  
Gas Phase ◽  
Excited States ◽  
Coupled Cluster ◽  
First Excited State ◽  
Guanine Base ◽  
High Level ◽  
Cluster Methods

High-level ab-initio equation-of-motion coupled-cluster methods with singles, doubles, and noniterative triples are used, in conjunction with the combined quantum mechanical molecular mechanics approach, to investigate the structure of low-lying excited states of the guanine base in DNA and solvated environments. Our results indicate that while the excitation energy of the first excited state is barely changed compared to its gas-phase counterpart, the excitation energy of the second excited state is blue-shifted by 0.24 eV.

Excited State Tracking During the Relaxation of Coordination Compounds

2018 ◽  
Author(s):  
Juan Sanz García ◽  
Martial Boggio-Pasqua ◽  
Ilaria Ciofini ◽  
Marco Campetella
Keyword(s):  
Excited State ◽  
Excited States ◽  
Potential Energy Surfaces ◽  
Photochemical Reactions ◽  
Complex Nature ◽  
Electronic Excited States ◽  
Ruthenium Nitrosyl ◽  
State Tracking ◽  
Energy Surfaces ◽  
Electronic Wavefunction

<div>The ability to locate minima on electronic excited states (ESs) potential energy surfaces (PESs) both in the case of bright and dark states is crucial for a full understanding of photochemical reactions. This task has become a standard practice for small- to medium-sized organic chromophores thanks to the constant developments in the field of computational photochemistry. However, this remains a very challenging effort when it comes to the optimization of ESs of transition metal complexes (TMCs), not only due to the presence of several electronic excited states close in energy, but also due to the complex nature of the excited states involved. In this article, we present a simple yet powerful method to follow an excited state of interest during a structural optimization in the case of TMC, based on the use of a compact hole-particle representation of the electronic transition, namely the natural transition orbitals (NTOs). State tracking using NTOs is unambiguously accomplished by computing the mono-electronic wavefunction overlap between consecutive steps of the optimization. Here, we demonstrate that this simple but robust procedure works not only in the case of the cytosine but also in the case of the ES optimization of a ruthenium-nitrosyl complex which is very problematic with standard approaches.</div>

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

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.

scholarly journals Two-electron transfer stabilized by excited-state aromatization

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Jinseok Kim ◽  
Juwon Oh ◽  
Seongchul Park ◽  
Jose L. Zafra ◽  
Justin R. DeFrancisco ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Excited States ◽  
Transfer Process ◽  
Comprehensive Understanding ◽  
Electron Transfer Process ◽  
Photoactive Materials ◽  
Donor Acceptor ◽  
Scientific Significance

Abstract The scientific significance of excited-state aromaticity concerns with the elucidation of processes and properties in the excited states. Here, we focus on TMTQ, an oligomer composed of a central 1,6-methano[10]annulene and 5-dicyanomethyl-thiophene peripheries (acceptor-donor-acceptor system), and investigate a two-electron transfer process dominantly stabilized by an aromatization in the low-energy lying excited state. Our spectroscopic measurements quantitatively observe the shift of two π-electrons between donor and acceptors. It is revealed that this two-electron transfer process accompanies the excited-state aromatization, producing a Baird aromatic 8π core annulene in TMTQ. Biradical character on each terminal dicyanomethylene group of TMTQ allows a pseudo triplet-like configuration on the 8π core annulene with multiexcitonic nature, which stabilizes the energetically unfavorable two-charge separated state by the formation of Baird aromatic core annulene. This finding provides a comprehensive understanding of the role of excited-state aromaticity and insight to designing functional photoactive materials.

scholarly journals Ultrafast and radiationless electronic excited state decay of uracil and thymine cations: computing the effects of dynamic electron correlation

2019 ◽  
Vol 21 (26) ◽  
pp. 14322-14330 ◽  
Author(s):  
Javier Segarra-Martí ◽  
Thierry Tran ◽  
Michael J. Bearpark
Keyword(s):  
Excited State ◽  
Excited States ◽  
Electron Correlation ◽  
Electronic Excited States ◽  
Electronic Excited State ◽  
State Decay ◽  
Radiationless Decay

In this article we characterise the radiationless decay of the first few electronic excited states of the cations of DNA/RNA nucleobases uracil and thymine, including the effects of dynamic electron correlation on energies and geometries (optimised with XMS-CASPT2).

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