Extrema of the density functional for the energy: Excited states from the ground-state theory

1985 ◽  
Vol 31 (10) ◽  
pp. 6264-6272 ◽  
Author(s):  
John P. Perdew ◽  
Mel Levy
2019 ◽  
Vol 75 (7) ◽  
pp. 985-989
Author(s):  
Wayne Hsu

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.


2012 ◽  
Vol 11 (03) ◽  
pp. 505-525 ◽  
Author(s):  
YUHUA ZHOU ◽  
KAI TAN ◽  
XIN LU

We have performed a systematic density functional study on the ground-state electronic structure and excited states of a representative D-σ-A dyad, i.e. EDT-TTF-Im-F4TCNQ π-radical, in vacuo and in different conventional solvents (toluene, THF, DMF and DMSO) by using some popular hybrid density functionals (B3LYP, M05, M05-2X, PBE0 and BMK). It has been shown that the M05 and B3LYP functionals perform the best in predicting the intramolecular charge-transfer (ICT) pertaining to both the ground state and excited states of the dyad. The amphoteric dyad is liable to solvent-promoted ICT from its EDT-TTF-Im donor (D) to F4TCNQ acceptor (A), adopting a charge-unseparated ground state D-A• in vacuo, a partially zwitterionic ground state [D-A]• in nonpolar toluene solvent, and a fully zwitterionic ground state D•+-A- in such polar solvents as THF, DMF and DMSO. Owing to its solvent-dependent chameleon ground state, excited states of the dyad in solvents also exhibit remarkable dependence on solvent polarity, as revealed by TDDFT calculations. Furthermore, cluster model calculations revealed that intermolecular charge-transfer readily occurs between the dyads, accounting for the observed zwitterionic charge state in solid state and solid-state semiconductivity.


2020 ◽  
Author(s):  
Tim Gould ◽  
Gianluca Stefanucci ◽  
Stefano Pittalis

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>


Author(s):  
Tim Gould ◽  
Gianluca Stefanucci ◽  
Stefano Pittalis

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.


2012 ◽  
Vol 11 (03) ◽  
pp. 651-661 ◽  
Author(s):  
R. P. DEKA ◽  
C. MEDHI

The proton assisted isomerization reactions of 1H-imidazo(4,5-b)pyridine (IMP) derivatives have been studied by using B3LYP/6-31G + (d,p) calculations, and the transition states of the reactions are analyzed with B3LYP/6-31+G(d,p) opt=qst3 route. It has been found that the prototropic transformation could be the feasible pathway of isomerization, since the energy gaps between the various protonated isomers are found closer compared to free molecules. The conversion of IMP-a1 to IMP-b1 may pass through several protrotopic isomerization, since the activation energy as well as the relative energy levels of these isomers are not small compared to other pathways. However, the results suggest that some of the reactions may take place simultaneously through protrotopic transformation. The relative variations of energy gaps in the excited states are smaller than the ground states. The protrotropic transformation in the excited states may be more feasible than the ground state.


Computation ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 59
Author(s):  
Ágnes Nagy

A time-independent density functional theory for excited states of Coulomb systems has recently been proposed in a series of papers. It has been revealed that the Coulomb density determines not only its Hamiltonian, but the degree of excitation as well. A universal functional valid for any excited state has been constructed. The excited-state Kohn–Sham equations bear resemblance to those of the ground-state theory. In this paper, it is studied how the excited-state functionals behave under coordinate scaling. A few relations for the scaled exchange, correlation, exchange-correlation, and kinetic functionals are presented. These relations are expected to be advantageous for designing approximate functionals.


2020 ◽  
Vol 16 ◽  
pp. 253
Author(s):  
S. Karatzikos ◽  
G. A. Lalazissis ◽  
R. Fossion ◽  
D. Peña-Arteaga ◽  
P. Ring

We propose a modification of the effective force NL3, which presents the very succesful parameterization for the Lagrangian of the Relativistic Mean Field (RMF) theory. The new effective force with the name NL3* has phenomenological para- meters. It improves the ground state properties of many nuclei and simultaneously provides an excellent description of excited states with collective character in sphe- rical and axially deformed nuclei.


2020 ◽  
Vol 85 (8) ◽  
pp. 1021-1032 ◽  
Author(s):  
Branislav Milovanovic ◽  
Milena Petkovic ◽  
Mihajlo Etinski

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.


2020 ◽  
Author(s):  
Tim Gould ◽  
Gianluca Stefanucci ◽  
Stefano Pittalis

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 working from a fluctuation dissipation theorem (FDT). 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>


2020 ◽  
Author(s):  
Tim Gould ◽  
Gianluca Stefanucci ◽  
Stefano Pittalis

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.


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