scholarly journals Equilibrium Geometries, Adiabatic Excitation Energies and Intrinsic C=C/C–H Bond Strengths of Ethylene in Lowest Singlet Excited States Described by TDDFT

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1545
Author(s):  
Yunwen Tao ◽  
Linyao Zhang ◽  
Wenli Zou ◽  
Elfi Kraka
Keyword(s):  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Excitation Energies ◽  
Functional Theory ◽  
Local Vibrational Mode ◽  
Strength Change ◽  
Bond Strengths ◽  
First Time ◽  
Equilibrium Geometries

Seventeen singlet excited states of ethylene have been calculated via time-dependent density functional theory (TDDFT) with the CAM-B3LYP functional and the geometries of 11 excited states were optimized successfully. The local vibrational mode theory was employed to examine the intrinsic C=C/C–H bond strengths and their change upon excitation. The natural transition orbital (NTO) analysis was used to further analyze the C=C/C–H bond strength change in excited states versus the ground state. For the first time, three excited states including πy′ → 3s, πy′ → 3py and πy′ → 3pz were identified with stronger C=C ethylene double bonds than in the ground state.

Multiconfiguration pair-density functional theory for doublet excitation energies and excited state geometries: the excited states of CN

2017 ◽  
Vol 19 (44) ◽  
pp. 30089-30096 ◽  
Author(s):  
Jie J. Bao ◽  
Laura Gagliardi ◽  
Donald G. Truhlar
Keyword(s):  
Density Functional Theory ◽  
Excited State ◽  
Excited States ◽  
Density Functional ◽  
Excitation Energies ◽  
Functional Theory ◽  
Pair Density

MC-PDFT is more accurate than CR-EOM-CCSD(T) or TDDFT when averaged over the first four adiabatic excitation energies of CN.

Can boron form coordination complexes with diffuse electrons? Evidence for linked solvated electron precursors

2022 ◽  
Author(s):  
Zachary Jordan ◽  
Shahriar N. Khan ◽  
Benjamin A. Jackson ◽  
Evangelos Miliordos
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Molecular System ◽  
Hydrocarbon Chain ◽  
Solvated Electron ◽  
Excitation Energies ◽  
Functional Theory ◽  
Boron Complexes ◽  
The Stability ◽  
First Time

Abstract Density functional theory and ab initio multi-reference calculations are performed to examine the stability and electronic structure of boron complexes that host diffuse electrons in their periphery. Such complexes (solvated electron precursors or SEPs) have been experimentally identified and studied theoretically for several s- and d-block metals. For the first time, we demonstrate that a p-block metalloid element can form a stable SEP when appropriate ligands are chosen. We show that three ammonia and one methyl ligands can displace two of the three boron valence electrons to a peripheral 1s-type orbital. The shell model for these outer electrons is identical to previous SEP systems (1s, 1p, 1d, 2s). Further, we preformed the first examination of a molecular system consisting of two SEPs bridged by a hydrocarbon chain. The electronic structure of these dimers is very similar to that of traditional diatomic molecules forming bonding and anti-bonding σ and π orbitals. Their ground state electronic structure resembles that of two He atoms, and our results indicate that the excitation energies are nearly independent of the chain length for four carbon atoms or longer. These findings pave the way for the development of novel materials similar to expanded metals and electrides.

INVESTIGATION OF DOMINANT ELECTRON CONFIGURATIONS IN TIME-DEPENDENT DENSITY FUNCTIONAL THEORY

2005 ◽  
Vol 04 (01) ◽  
pp. 265-280 ◽  
Author(s):  
SUSUMU YANAGISAWA ◽  
TAKAO TSUNEDA ◽  
KIMIHIKO HIRAO
Keyword(s):  
Density Functional Theory ◽  
Small Molecules ◽  
Excited States ◽  
Density Functional ◽  
Time Dependent ◽  
Response Matrix ◽  
Excitation Energies ◽  
Functional Theory ◽  
Electron Transitions ◽  
Dependent Density

We investigated the electron configurations that are dominant in excited states of molecules in time-dependent density functional theory (TDDFT). By taking advantage of the discussion on off-diagonal elements in the TDDFT response matrix (Appel et al., Phys Rev Lett, 90, 043005, 2003), we can pick up electron transitions that contribute to an excitation of interest by making use of the diagonal elements of the TDDFT matrix. We can obtain approximate excitation energies by calculating a TDDFT submatrix, which is contracted for a list of collected transitions. This contracted TDDFT was applied to the calculation of excitation energies of the CO molecule adsorbing Pt 10 cluster and some prototype small molecules. Calculated results showed that a TDDFT excitation energy is dominated by a few electron configurations, unless severe degeneracy is involved.

Luminescence properties and optimized structural conformations of the S0, S1 and T1 states of a tetranuclear formamidinate complex based on AuI and AgI metal ions

2019 ◽  
Vol 75 (7) ◽  
pp. 985-989
Author(s):  
Wayne Hsu
Keyword(s):  
Metal Ions ◽  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Metal Salts ◽  
Time Dependent ◽  
Functional Theory ◽  
Planar Conformation ◽  
Ligand Charge Transfer ◽  
Td Dft

N,N′-Bis(pyridin-4-yl)formamidine (4-pyfH) was reacted with AuI and AgI metal salts to form a novel tetranuclear complex, tetrakis[μ-N,N′-bis(pyridin-4-yl)formamidinato]digold(I)disilver(I), [Ag2Au2(C11H9N4)2] or [Au x Ag4–x (4-pyf)4] (x = 0–4), 1, which is supported by its metallophilicity. Due to the potential permutation of the coordinated metal ions, six different canonical structures of 1 can be obtained. Complex 1 shows an emission at 501 nm upon excitation at 375 nm in the solid state and an emission at 438 nm upon excitation at 304 nm when dispersed in methanol. Time-dependent density functional theory (TD-DFT) calculations confirmed that these emissions can be ascribed to metal-to-ligand charge transfer (MLCT) processes. Moreover, the calculations of the optimized structural conformations of the S0 ground state, and the S1 and T1 excited states are discussed and suggest a distorted planar conformation for the tetranuclear Au2Ag2 complex.

scholarly journals Ensemble Density Functional Theory Reloaded

2020 ◽  
Author(s):  
Tim Gould ◽  
Gianluca Stefanucci ◽  
Stefano Pittalis
Keyword(s):  
Density Functional Theory ◽  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Low Cost ◽  
Ground States ◽  
Exchange Energy ◽  
Functional Theory ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem

Density functional theory can be generalized to mixtures of ground and excited states, for the purpose of determining energies of excitations using low-cost density functional approximations. Adapting approximations originally developed for ground states to work in the new setting would fast-forward progress enormously. But, previous attempts have stumbled on daunting fundamental issues. Here we show that these issues can be prevented from the outset, by using a fluctuation dissipation theorem (FDT) to dictate key functionals. We thereby show that existing exchange energy approximations are readily adapted to excited states, when combined with a rigorous exact Hartree term that is different in form from its ground state counterpart, and counterparts based on ensemble ansatze. Applying the FDT to correlation energies also provides insights into ground state-like and ensemble-only correlations. We thus provide a comprehensive and versatile framework for ensemble density functional approximations.<br><br>

scholarly journals Ensemblization of density-functional theory: Insight from the fluctuation-dissipation theorem

2020 ◽  
Author(s):  
Tim Gould ◽  
Gianluca Stefanucci ◽  
Stefano Pittalis
Keyword(s):  
Density Functional Theory ◽  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Low Cost ◽  
Ground States ◽  
Exchange Energy ◽  
Functional Theory ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem

Density functional theory can be generalized to mixtures of ground and excited states, for the purpose of determining energies of excitations using low-cost density functional approximations. Adapting approximations originally developed for ground states to work in the new setting would fast-forward progress enormously. But, previous attempts have stumbled on daunting fundamental issues. Here we show that these issues can be prevented from the outset, by using a fluctuation dissipation theorem (FDT) to dictate key functionals. We thereby show that existing exchange energy approximations are readily adapted to excited states, when combined with a rigorous exact Hartree term that is different in form from its ground state counterpart, and counterparts based on ensemble ansatze. Applying the FDT to correlation energies also provides insights into ground state-like and ensemble-only correlations. We thus provide a comprehensive and versatile framework for ensemble density functional approximations.

scholarly journals Properties of the excited electronic states of guanine quartet complexes with alkali metal cations

2020 ◽  
Vol 85 (8) ◽  
pp. 1021-1032 ◽  
Author(s):  
Branislav Milovanovic ◽  
Milena Petkovic ◽  
Mihajlo Etinski
Keyword(s):  
Excited States ◽  
Ground State ◽  
Density Functional ◽  
Fluorescence Spectra ◽  
Metal Cations ◽  
Molecular Structures ◽  
Alkali Metal Cations ◽  
Functional Theory ◽  
Guanine Quartet ◽  
Sodium And Potassium

G-quartets are supra-molecular structures that consist of four guanine molecules connected by eight hydrogen bonds. They are additionally stabilized by metal cations. In this contribution, the excited states of G-quartet and its complexes with lithium, sodium and potassium were studied by employing time-dependent density functional theory. The findings indicate that vertical excitations from the optimized ground state involve transitions from several bases, whereas excitations from the optimized lowest excited state include transitions from one base. The charge-transfer character of these states was analyzed. It was shown that the cations are able to modify positions of the maxima of the fluorescence spectra of the complexes.

Sign in / Sign up

Export Citation Format

Share Document