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.

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>

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 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>

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.

The X40x10 Halogen Bonding Benchmark Revisited: Surprising Importance of (n-1)d Subvalence Correlation

2017 ◽  
Author(s):  
Manoj Kumar Kesharwani ◽  
Nitai Sylvetsky ◽  
Debashree Manna ◽  
Jan M.L. Martin
Keyword(s):  
Dissociation Energy ◽  
Noncovalent Interactions ◽  
Halogen Bonding ◽  
Coupled Cluster ◽  
Dissociation Energies ◽  
Iodine Species ◽  
Explicitly Correlated ◽  
High Level ◽  
Cluster Methods ◽  
Small Separation

<p>We have re-evaluated the X40x10 benchmark for halogen bonding using conventional and explicitly correlated coupled cluster methods. For the aromatic dimers at small separation, improved CCSD(T)–MP2 “high-level corrections” (HLCs) cause substantial reductions in the dissociation energy. For the bromine and iodine species, (n-1)d subvalence correlation increases dissociation energies, and turns out to be more important for noncovalent interactions than is generally realized. As in previous studies, we find that the most efficient way to obtain HLCs is to combine (T) from conventional CCSD(T) calculations with explicitly correlated CCSD-F12–MP2-F12 differences.</p>

scholarly journals A computational study for the reaction mechanism of metal-free cyanomethylation of aryl alkynoates with acetonitrile

RSC Advances ◽  
2021 ◽  
Vol 11 (30) ◽  
pp. 18246-18251
Author(s):  
Selçuk Eşsiz
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Density Functional ◽  
Computational Study ◽  
Coupled Cluster ◽  
Functional Theory ◽  
Metal Free ◽  
Coupled Cluster Methods ◽  
High Level ◽  
Cluster Methods

A computational study of metal-free cyanomethylation and cyclization of aryl alkynoates with acetonitrile is carried out employing density functional theory and high-level coupled-cluster methods, such as [CCSD(T)].

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.

scholarly journals A New Benchmark Set for Excitation Energy of Charge Transfer States: Systematic Investigation of Coupled-Cluster Type Methods

2020 ◽  
Author(s):  
Balázs Kozma ◽  
Attila Tajti ◽  
Baptiste Demoulin ◽  
Róbert Izsák ◽  
Marcel Nooijen ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Excitation Energy ◽  
Systematic Investigation ◽  
Coupled Cluster ◽  
Excitation Energies ◽  
Chemical Methods ◽  
Valence States ◽  
Quantum Chemical Methods ◽  
Material Physics ◽  
Cluster Methods

There are numerous publications on benchmarking quantum chemistry methods for excited states. These studies rarely include Charge Transfer (CT) states although many interesting phenomena in e.g. biochemistry and material physics involve transfer of electron between fragments of the system. Therefore, it is timely to test the accuracy of quantum chemical methods for CT states, as well. In this study we first suggest a set benchmark systems consisting of dimers having low-energy CT states. On this set, the excitation energy has been calculated with coupled cluster methods including triple excitations (CC3, CCSDT-3, CCSD(T)(a)* ), as well as with methods including full or approximate doubles (CCSD, STEOM-CCSD, CC2, ADC(2), EOM-CCSD(2)). The results show that the popular CC2 and ADC(2) methods are much more inaccurate for CT states than for valence states. On the other hand, CCSD seems to have similar systematic overestimation of the excitation energies for both valence and CT states. Concerning triples methods, the new CCSD(T)(a)* method including non-iterative triple excitations preforms very well for all type of states, delivering essentially CCSDT quality results.<br>

scholarly journals GDR Contribution to Coulomb Excitation. II. 17O

1982 ◽  
Vol 35 (3) ◽  
pp. 301 ◽  
Author(s):  
FC Barker
Keyword(s):  
Excited State ◽  
Shell Model ◽  
Excited States ◽  
Giant Dipole Resonance ◽  
Coulomb Excitation ◽  
Dipole Resonance ◽  
First Excited State ◽  
Virtual Excitation

The contribution to the Coulomb excitation of the first excited state of 170 due to virtual excitation of the giant dipole resonance (GDR) is calculated, using shell model wavefunctions for the ground and first excited states. A large value is obtained.

Sign in / Sign up

Export Citation Format

Share Document