Communication: An inexpensive, variational, almost black-box, almost size-consistent correction to configuration interaction singles for valence excited states

Liu, Xinle; Ou, Qi; Alguire, Ethan; Subotnik, Joseph E.

doi:10.1063/1.4809571

Cited by 20 publications

(35 citation statements)

References 17 publications

(15 reference statements)

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“…This relaxation effect is probably related to an extended charge shift in this state (as seen by the dipole moment μ = 2.90 D), see, e.g., Ref. 31. Finally, it is interesting to compare the pictorial representation of the attachment density ( Figure 4) with the one of the particle density ( Figure 3): the particle density closely resembles the relevant π * MO while the attachment density possesses a notable additional contribution on the N-atom, in accordance to the previous discussion.…”

Section: Detachment Attachmentmentioning

confidence: 88%

New tools for the systematic analysis and visualization of electronic excitations. II. Applications

Plasser

Bäppler

Wormit

et al. 2014

The Journal of Chemical Physics

238

320

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Electronic spectroscopy of toluene-rare-gas clusters: The external heavy atom effect and vibrational predissociationThe excited states of a diverse set of molecules are examined using a collection of newly implemented analysis methods. These examples expose the particular power of three of these tools: (i) natural difference orbitals (the eigenvectors of the difference density matrix) for the description of orbital relaxation effects, (ii) analysis of the one-electron transition density matrix in terms of an electronhole picture to identify charge resonance and excitonic correlation effects, and (iii) state-averaged natural transition orbitals for a compact simultaneous representation of several states. Furthermore, the utility of a wide array of additional analysis methods is highlighted. Five molecules with diverse excited state characteristics are chosen for these tasks: pyridine as a prototypical small heteroaromatic molecule, a model system of six neon atoms to study charge resonance effects, hexatriene in its neutral and radical cation forms to exemplify the cases of double excitations and spin-polarization, respectively, and a model iridium complex as a representative metal organic compound. Using these examples a number of phenomena, which are at first sight unexpected, are highlighted and their physical significance is discussed. Moreover, the generality of the conclusions of this paper is verified by a comparison of single-and multireference ab initio methods. © 2014 AIP Publishing LLC.

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Section: Detachment Attachmentmentioning

confidence: 88%

New tools for the systematic analysis and visualization of electronic excitations. II. Applications

Plasser

Bäppler

Wormit

et al. 2014

The Journal of Chemical Physics

238

320

View full text Add to dashboard Cite

show abstract

“…Furthermore, low-cost methods improving on CIS have recently been proposed by Subotnik and co-workers. [13][14][15] Another class of methods can be thought of as stabilizing charge-localized solutions by introducing (explicit or implicit) constraints in the electronic-structure calculation. Typically, self-consistent field (SCF) calculations will not converge to charge-separated solutions, as these are energetically unfavorable and correspond to "excited" configurations of the system unless stabilized by external effects.…”

Section: Introductionmentioning

confidence: 99%

Describing long-range charge-separation processes with subsystem density-functional theory

Solovyeva

Pavanello

Neugebauer

2014

The Journal of Chemical Physics

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Long-range charge-transfer processes in extended systems are difficult to describe with quantum chemical methods. In particular, cost-effective (non-hybrid) approximations within time-dependent density functional theory (DFT) are not applicable unless special precautions are taken. Here, we show that the efficient subsystem DFT can be employed as a constrained DFT variant to describe the energetics of long-range charge-separation processes. A formal analysis of the energy components in subsystem DFT for such excitation energies is presented, which demonstrates that both the distance dependence and the long-range limit are correctly described. In addition, electronic couplings for these processes as needed for rate constants in Marcus theory can be obtained from this method. It is shown that the electronic structure of charge-separated states constructed by a positively charged subsystem interacting with a negatively charged one is difficult to converge - charge leaking from the negative subsystem to the positive one can occur. This problem is related to the delocalization error in DFT and can be overcome with asymptotically correct exchange-correlation (XC) potentials or XC potentials including a sufficiently large amount of exact exchange. We also outline an approximate way to obtain charge-transfer couplings between locally excited and charge-separated states.

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“…Classification 109 and charge transfer states, particularly in transition metal complexes. 55 Methodologically speaking, states with larger p values require additional flexibility in the wavefunction description but it might suffice to use an orbital-optimised version of the CIS method 126 rather than a truly dynamically correlated method. The final class of states, identified by nonvanishing P he values, corresponds to states with significant deexcitation character.…”

Section: Conditionmentioning

confidence: 99%

Toward an Understanding of Electronic Excitation Energies Beyond the Molecular Orbital Picture

Kimber¹,

Plasser²

2020

Preprint

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<pre><div><div><div><p>Tuning the energies of molecular excited states is a central research theme in modern chemistry with high relevance for optoelectronic applications and chemical synthesis. Whereas frontier orbitals have proven to be an intuitive and simple model in many cases, they can only provide a very rough approximation of the underlying wavefunctions. The purpose of this Perspective is to explore how our qualitative understanding of electronic excitation processes can be promoted beyond the molecular orbital picture by exploiting methods and insights from modern quantum chemistry. For this purpose, the physics of a correlated electron-hole pair is analysed in detail to show the origin of exchange repulsion and a dynamic Coulomb attraction, which determine its energy aside from the orbital energies. Furthermore, we identify and discuss the two additional effects of secondary orbital relaxation and de-excitations. Rules for reconstructing these four contributions from general excited-state computations are presented and their use is exem- plified in three case studies concerned with the relative ordering of the singlet and triplet ππ∗ and nπ∗ states of uracil, the large energetic differences between the first singlet and triplet states of the polyacenes, and the assignment of plasmonic states in octatetraene. Finally, we lay out some general ideas for how the knowledge gained could ultimately lead to new design principles for tuning molecular excitation energies as well as for diagnosing possible shortcomings of commonly used electronic structure methods.</p></div></div></div></pre>

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Communication: An inexpensive, variational, almost black-box, almost size-consistent correction to configuration interaction singles for valence excited states

Cited by 20 publications

References 17 publications

New tools for the systematic analysis and visualization of electronic excitations. II. Applications

New tools for the systematic analysis and visualization of electronic excitations. II. Applications

Describing long-range charge-separation processes with subsystem density-functional theory

Toward an Understanding of Electronic Excitation Energies Beyond the Molecular Orbital Picture

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