Entanglement entropy of electronic excitations

© 2016 Author(s). A new perspective into correlation effects in electronically excited states is provided through quantum information theory. The entanglement between the electron and hole quasiparticles is examined, and it is shown that the related entanglement entropy can be computed from the eigenvalue spectrum of the well-known natural transition orbital (NTO) decomposition. Non-vanishing entanglement is obtained whenever more than one NTO pair is involved, i.e., in the case of a multiconfigurational or collective excitation. An important implication is that in the case of entanglement it is not possible to gain a complete description of the state character from the orbitals alone, but more specific analysis methods are required to decode the mutual information between the electron and hole. Moreover, the newly introduced number of entangled states is an important property by itself giving information about excitonic structure. The utility of the formalism is illustrated in the cases of the excited states of two interacting ethylene molecules, the conjugated polymer para-phenylene vinylene, and the naphthalene molecule

Visualisation of electronic excited-state correlation in real space

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

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

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 densitie

Quantitative wave function analysis for excited states of transition metal complexes

The character of an electronically excited state is one of the most important descriptors employed to discuss the photophysics and photochemistry of transition metal complexes. In transition metal complexes, the interaction between the metal and the different ligands gives rise to a rich variety of excited states, including metal-centered, intra-ligand, metal-to-ligand charge transfer, ligand-to-metal charge transfer, and ligand-to-ligand charge transfer states. Most often, these excited states are identified by considering the most important wave function excitation coefficients and inspecting visually the involved orbitals. This procedure is tedious, subjective, and imprecise. Instead, automatic and quantitative techniques for excited-state characterization are desirable. In this contribution we review the concept of charge transfer numbers---as implemented in the TheoDORE package---and show its wide applicability to characterize the excited states of transition metal complexes. Charge transfer numbers are a formal way to analyze an excited state in terms of electron transitions between groups of atoms based only on the well-defined transition density matrix. Its advantages are many: it can be fully automatized for many excited states, is objective and reproducible, and provides quantitative data useful for the discussion of trends or patterns. We also introduce a formalism for spin-orbit-mixed states and a method for statistical analysis of charge transfer numbers. The potential of this technique is demonstrated for a number of prototypical transition metal complexes containing Ir, Ru, and Re. Topics discussed include orbital delocalization between metal and carbonyl ligands, nonradiative decay through metal-centered states, effect of spin-orbit couplings on state character, and comparison among results obtained from different electronic structure methods.Comment: 47 pages, 19 figures, including supporting information (7 pages, 1 figure

Interstate Vibronic Coupling Constants Between Electronic Excited States for Complex Molecules

In the construction of diabatic vibronic Hamiltonians for quantum dynamics in the excited-state manifold of molecules, the coupling constants are often extracted solely from information on the excited-state energies. Here, a new protocol is applied to get access to the interstate vibronic coupling constants at the time-dependent density functional theory level through the overlap integrals between excited-state adiabatic auxiliary wavefunctions. We discuss the advantages of such method and its potential for future applications to address complex systems, in particular those where multiple electronic states are energetically closely lying and interact. As examples, we apply the protocol to the study of prototype rhenium carbonyl complexes [Re(CO)$_3$(N,N)(L)]$^{n+}$ for which non-adiabatic quantum dynamics within the linear vibronic coupling model and including spin-orbit coupling have been reported recently.Comment: 36 pages, 7 figures, 4 table

The Schüssel Era in Austria

Wolfgang Schüssel was a dominating actor in the Austrian political arena over a period of twenty years. He served as minister of economics (1989-1995), and vice chancellor and foreign minister (1995-2000) in ÖVP/SPÖ grand coalition governments. As chairman of the ÖVP (1995-2007), he brought his conservative party out of the political wilderness of opposition and playing junior partner in coalitions with the SPÖ. He dominated Austrian politics as chancellor (2000-2007) in a small coalition with Jörg Haider’s controversial aggressively nationalist FPÖ. Schüssel tried to domesticate the Freedomites by holding them on a tight leash in his coalition government. He needed the FPÖ to accomplish his neoliberal economic and social reform agenda, while at the same time the FPÖ undermined Schüssel’s EU policies. The essays in this volume argue that Schüssel’s political record and legacy are ambiguous. With a confrontational style of governance he unleashed big reforms such as trimming the hidebound pension system and giving more autonomy to higher education. In the process he undermined Austria’s consensual social partnership. His record of supporting the European Union agenda is ambivalent. Austrian public opinion in support of the EU declined precipitously. He was a superb tactician and negotiator yet failed to achieve broad popular acceptance for his ambitious reforms. His imprint on Austrian history is so significant that many of the authors of the essays in this volume call it “the Schüssel era.

Communication: Unambiguous comparison of many-electron wavefunctions through their overlaps

© 2016 Author(s). A simple and powerful method for comparing many-electron wavefunctions constructed at different levels of theory is presented. By using wavefunction overlaps, it is possible to analyze the effects of varying wavefunction models, molecular orbitals, and one-electron basis sets. The computation of wavefunction overlaps eliminates the inherent ambiguity connected to more rudimentary wavefunction analysis protocols, such as visualization of orbitals or comparing selected physical observables. Instead, wavefunction overlaps allow processing the many-electron wavefunctions in their full inherent complexity. The presented method is particularly effective for excited state calculations as it allows for automatic monitoring of changes in the ordering of the excited states. A numerical demonstration based on multireference computations of two test systems, the selenoacrolein molecule and an iridium complex, is presented

The Seaway Tracker Project

The purpose of this paper is to introduce an interpretation model for the deployment of new media in didactics, taking inspiration from theories coming both from Didactics and Semiotics. State of the art experiences are analysed, in order to evaluate and settle novelties and limits in an adequate context. Finally, the project of a new didactic system is described. This system takes advantage from the expert systems technology and from the latest media format research (MPEG-4 and MPEG-7). It exploits the potential of the new media in terms of enhanced dynamic hypertext navigation and interactivity through the use of semantic data

Uv absorption inmetal decorated boron nitride flakes: A theoretical analysis of excited states

© Informa UK Limited, trading as Taylor & Francis Group. The excited states of singlemetal atom(X=Co, Al and Cu) doped boron nitride flake (MBNF) B 15 N 14 H 14 -X and pristine boron nitride (B 15 N 15 H 14 ) are studied by time-dependent density functional theory. The immediate effect of metal doping is a red shift of the onset of absorption from about 220 nmfor pristine BNF to above 300 nm for all metal-doped variants with the biggest effect for MBNF-Co, which shows appreciable intensity even above 400 nm. These energy shifts are analysed by detailed wavefunction analysis protocols using visualisationmethods, such as the natural transition orbital analysis and electron-hole correlation plots, as well as quantitative analysis of the exciton size and electronhole populations. The analysis shows that the Co and Cu atoms provide strong contributions to the relevant states whereas the aluminium atom is only involved to a lesser extent

Dynamics simulation of excited state intramolecular proton transfer

Der doppelte Protonentransfer von [2,2'-bipyridyl-]-3,3'-diol im angeregten Zustand wurde mit Hilfe von ab-initio Molekulardynamik simuliert. Die zeitabhängigen experimentellen Spektren konnten gut reproduziert werden. Die Simulation erlaubte es, den Prozess direkt zu beobachten und das Verständnis der Reaktion zu verfeinern. Insbesondere wurde beobachtet, dass das System dynamischer ist als bisher angenommen und keine zwei getrennten Reaktionswege für Einfach- und Doppeltransfer vorliegen.The excited state double proton transfer of [2,2'-bipyridyl-]-3,3'-diol was simulated with ab-initio molecular dynamics simulations. Through this the time-dependent experimental spectra could be well reproduced. The simulation gave the possibility to directly observe the process and improve the understanding of this reaction. Particularly it was observed that the system is highly dynamical and that there are not two separate reaction branches for single and double transfer