Excitation Number: Characterizing Multiply Excited States

Barca, Giuseppe M. J.; Gilbert, Andrew T. B.; Gill, Peter M. W.

doi:10.1021/acs.jctc.7b00963

Cited by 67 publications

(105 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, a considerable effort has been devoted to the development of methods for analysing electronic structure computations with the aims of automatising excited-state analysis, making it reproducible, and revealing phenomena that are hidden in the standard molecular orbital (MO) picture. These methods encompass visualisation techniques [6][7][8] while also a number quantitative descriptors have been designed measuring charge-transfer (CT), [9][10][11][12][13] double excitation character, 8,[14][15][16] and entanglement. [17][18][19][20] A particular effort has been devoted to the task of visualising excited-state correlations using correlation plots [21][22][23][24][25][26] and conditional densities.…”

Section: Introductionmentioning

confidence: 99%

TheoDORE: A toolbox for a detailed and automated analysis of electronic excited state computations

Plasser

2020

The Journal of Chemical Physics

300

354

View full text Add to dashboard Cite

The advent of ever more powerful excited-state electronic structure methods has lead to a tremendous increase in the predictive power of computation but it has also rendered the analysis of these computations more and more challenging and time-consuming. TheoDORE tackles this problem through providing tools for post-processing excited-state computations, which automate repetitive tasks and provide rigorous and reproducible descriptors. Interfaces are available for ten different quantum chemistry codes and a range of excited-state methods implemented therein. This article provides an overview of three popular functionalities within TheoDORE, a fragment-based analysis for assigning state character, the computation of exciton sizes for measuring charge transfer, and the natural transition orbitals used not only for visualisation but also for quantifying multiconfigurational character. Using the examples of an organic push-pull chromophore and a transition metal complex, it is shown how these tools can be used for a rigorous and automated assignment of excited-state character. In the case of a conjugated polymer, we venture beyond the limits of the traditional molecular orbital picture to uncover spatial correlation effects using electron-hole correlation plots and conditional densities.

show abstract

Section: Introductionmentioning

confidence: 99%

TheoDORE: A toolbox for a detailed and automated analysis of electronic excited state computations

Plasser

2020

The Journal of Chemical Physics

300

354

View full text Add to dashboard Cite

show abstract

“…∆SCF ∆SCF 67,68 methods converge a single Slater determinant as an excited state solution to the HF/KS equations. The likelihood of variational collapse had long restricted the utility of ∆SCF, but the development of MOM led to a revival of interest in the method 25,39,68,69. …”

mentioning

confidence: 99%

Excited State Orbital Optimization via Minimizing the Square of the Gradient: General Approach and Application to Singly and Doubly Excited States via Density Functional Theory

Hait

Head‐Gordon

2020

J. Chem. Theory Comput.

164

297

View full text Add to dashboard Cite

We present a general approach to converge excited state solutions to any quantum chemistry orbital optimization process, without the risk of variational collapse.The resulting Square Gradient Minimization (SGM) approach only requires analytic energy/Lagrangian orbital gradients and merely costs 3 times as much as ground state orbital optimization (per iteration), when implemented via a finite difference approach.SGM is applied to both single determinant ∆SCF and spin-purified Restricted Open-Shell Kohn-Sham (ROKS) approaches to study the accuracy of orbital optimized DFT excited states. It is found that SGM can converge challenging states where the Maximum Overlap Method (MOM) or analogues either collapse to the ground state or fail to converge. We also report that ∆SCF/ROKS predict highly accurate excitation 1 arXiv:1911.04709v1 [physics.chem-ph] 12 Nov 2019 energies for doubly excited states (which are inaccessible via TDDFT). Singly excited states obtained via ROKS are also found to be quite accurate, especially for Rydberg states that frustrate (semi)local TDDFT. Our results suggest that orbital optimized excited state DFT methods can be used to push past the limitations of TDDFT to doubly excited, charge-transfer or Rydberg states, making them a useful tool for the practical quantum chemist's toolbox for studying excited states in large systems. IntroductionAccurate quantum chemical methods for modeling electronic excited states are essential for gaining insight into the photophysics and photochemistry of molecules and materials. The most widely used technique for excited state calculations at present is time dependent density functional theory (TDDFT), 1-5 on account of its relatively low computational complexity (O(N 2−3 ), where N is the molecule size) and reasonable accuracy for many problems. 6,7 TDDFT excited states are computed via determining the linear response of a ground state DFT solution to time-dependent external electric fields, 5 permitting simultaneous modeling of multiple excited states. In principle, TDDFT is formally exact 1 when the exact exchangecorrelation (xc) ground state functional is employed, although lack of that functional, and the need for the widely used adiabatic local density approximation 3-5 (ALDA) prevents this from being the case in practice. ALDA in fact restricts utility of TDDFT to single excitations out of the reference alone, with large errors arising whenever the target excited state has significant double (or higher) excitation character. 8-11 Furthermore, TDDFT is known to systematically underestimate excitation energies for charge-transfer 5,12-14 and Rydberg 8,15 states, and yields qualitatively erroneous potential energy surfaces along single bond dissociation coordinates. 16 These effects originally stem from errors in the ground state DFT solution like delocalization error 17,18 or spin symmetry breaking, 19,20 but the linear response protocol augments these deficiencies in the reference to catastrophic levels in excited states, on account of insufficient or...

show abstract

“…The application of this approach to oligothiophene, an exemplary conjugated polymer, illuminates excitonic correlation effects of its excited states in unprecedented clarity and detail. Therefore, a number of analysis tools have been developed to quantify excited-state properties [13][14][15][16][17] and to visualise the molecular orbitals (MOs) involved and their location in space in a compact and rigorous way. More generally, the method is relevant for any excited state that cannot be described by a single electronic configuration.…”

mentioning

confidence: 99%

“…Indeed, the predictive power of computational photochemistry has steadily increased over the recent years due to the tremendous effort spent in the development of new methods as well as rapid progress in computer technology. Therefore, a number of analysis tools have been developed to quantify excited-state properties [13][14][15][16][17] and to visualise the molecular orbitals (MOs) involved and their location in space in a compact and rigorous way. Therefore, a number of analysis tools have been developed to quantify excited-state properties [13][14][15][16][17] and to visualise the molecular orbitals (MOs) involved and their location in space in a compact and rigorous way.…”

mentioning

confidence: 99%

Visualisation of Electronic Excited‐State Correlation in Real Space

Plasser

2019

ChemPhotoChem

View full text Add to dashboard Cite

A method for the visualisation of excited-state electron correlation is introduced and shown to address two notorious problems in excited-state electronic structure theory, the analysis of excitonic correlation and the distinction between covalent and ionic wavefunction character. The method operates by representing the excited state in terms of electron and hole quasiparticles, fixing the hole on a fragment of the system and observing the resulting conditional electron density in real space. The application of this approach to oligothiophene, an exemplary conjugated polymer, illuminates excitonic correlation effects of its excited states in unprecedented clarity and detail. A study of naphthalene shows that the distinction between the ionic and covalent states of this molecule, which has so far only been achieved using elaborate valence-bond theory protocols, arises naturally in terms of electron-hole avoidance and enhanced overlap, respectively. More generally, the method is relevant for any excited state that cannot be described by a single electronic configuration.Electronically excited states of molecules form the underpinnings of a wide range of processes of utmost scientific interest, such as light-driven natural processes [1,2] photochemical reactions, [3] signalling and sensing, [4] and the operation of organoelectronic materials. [5,6] Computational photochemistry has become an indispensable part of scientific investigations in these areas through two main tasks, the interpretation of experimental results and the prediction of unknown photophysical properties. Indeed, the predictive power of computational photochemistry has steadily increased over the recent years due to the tremendous effort spent in the development of new methods as well as rapid progress in computer technology. [7][8][9][10][11][12] However, the interpretation of this wealth of computational data can act as a significant impediment in practical work. Therefore, a number of analysis tools have been developed to quantify excited-state properties [13][14][15][16][17] and to visualise the molecular orbitals (MOs) involved and their location in space in a compact and rigorous way. [18][19][20][21][22][23] However, the above-mentioned visualisation tools -and the MO picture itself -break down if the information of interest does not lie in the MOs themselves but in the interaction of different quasidegenerate electronic configurations. Such cases are widespread and two notorious failures of the MO picture relate to excitons in extended systems [24][25][26] and to ionic/ covalent wavefunction character in alternant hydrocarbons. [27,28] The first case is related to the emergence of band structure in large systems, which leads to excited states formed as a superposition of many different electronic configurations whose description requires moving from the MO picture to a representation in terms of correlated electron and hole quasiparticles. [26,[29][30][31] Previous attempts of visualising the ensuing correlated electron-hole distribution ha...

show abstract

Excitation Number: Characterizing Multiply Excited States

Cited by 67 publications

References 47 publications

TheoDORE: A toolbox for a detailed and automated analysis of electronic excited state computations

TheoDORE: A toolbox for a detailed and automated analysis of electronic excited state computations

Excited State Orbital Optimization via Minimizing the Square of the Gradient: General Approach and Application to Singly and Doubly Excited States via Density Functional Theory

Visualisation of Electronic Excited‐State Correlation in Real Space

Contact Info

Product

Resources

About