Michael A. Robb
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Coherent Excitation of the <span>CH</span> Stretching Vibrations in <span> C <sub>2</sub> H <sub>4</sub> </span> <sup>+</sup> : The Role of the Derivative Coupling Studied by the Quantum Ehrenfest Method Open
We report nonadiabatic dynamics computations on C 2 H 4 + initiated on a coherent superposition of the five lowest cationic states, employing the Quantum Ehrenfest method. In addition to the totally symmetric carbon–carbon double bond stre…
Real-Time CASSCF (Ehrenfest) Modeling of Electron Dynamics in Organic Semiconductors. Dynamics Reaction Paths Driven by Quantum Coherences. Application to a Radical Organic Semiconductor Open
We present a strategy for the modeling of charge carrier dynamics in organic semiconductors using conventional quantum chemistry methods, including the analytic gradient for nuclear motion. The theoretical approach uses real-time CASSCF (E…
Controlling Electronic Coherences and the Curvature Induced by the Derivative Coupling at a Conical Intersection: A Quantum Ehrenfest (QuEh) Protocol for Reaction Path Following Application to “Channel 3” Benzene Photochemistry Open
We report a protocol for the implementation of "reaction path following" from a transition state through a conical intersection, including both the path curvature induced by the derivative coupling and the corresponding induced electronic …
Using ‘designer’ coherences to control electron transfer in a model bis(hydrazine) radical cation: can we still distinguish between direct and superexchange mechanisms? Open
We have simulated two mechanisms, direct and superexchange, for the electron transfer in a model Bis(hydrazine) Radical Cation , which consists of two hydrazine moieties coupled by a benzene ring. The computations, that are inspired by the…
Coherent Mixing of Singlet and Triplet States in Acrolein and Ketene: A Computational Strategy for Simulating the Electron–Nuclear Dynamics of Intersystem Crossing Open
We present a theoretical study of intersystem crossing (ISC) in acrolein and ketene with the Ehrenfest method that can describe a superposition of singlet and triplet states. Our simulations illustrate a new mechanistic effect of ISC, name…
How electronic superpositions drive nuclear motion following the creation of a localized hole in the glycine radical cation Open
In this work, we have studied the nuclear and electron dynamics in the glycine cation starting from localized hole states using the quantum Ehrenfest method. The nuclear dynamics is controlled both by the initial gradient and by the instan…
View article: Correlation-Driven Transient Hole Dynamics Resolved in Space and Time in the Isopropanol Molecule
Correlation-Driven Transient Hole Dynamics Resolved in Space and Time in the Isopropanol Molecule Open
The possibility of suddenly ionized molecules undergoing extremely fast electron hole dynamics prior to significant structural change was first recognized more than 20 years ago and termed charge migration. The accurate probing of ultrafas…
Unlocking the Double Bond in Protonated Schiff Bases by Coherent Superposition of S<sub>1</sub> and S<sub>2</sub> Open
The primary event occurring during the E-to-Z photoisomerization reaction of retinal protonated Schiff base (rPSB) is single-to-double bond inversion. In this work we examine the nuclear dynamics that occurs when the initial excited state …
Molecular Vertical Excitation Energies Studied with First-Order RASSCF (RAS[1,1]): Balancing Covalent and Ionic Excited States Open
RASSCF calculations of vertical excitation energies were carried out on a benchmark set of 19 organic molecules studied by Thiel and co-workers [ J. Chem. Phys. 2008 , 128 , 134110 ]. The best results, in comparison with the MS-CASPT2 resu…
The Ehrenfest method with fully quantum nuclear motion (Qu-Eh): Application to charge migration in radical cations Open
An algorithm is described for quantum dynamics where an Ehrenfest potential is combined with fully quantum nuclear motion (Quantum-Ehrenfest, Qu-Eh). The method is related to the single-set variational multi-configuration Gaussian approach…
Charge migration engineered by localisation: electron-nuclear dynamics in polyenes and glycine Open
We demonstrate that charge migration can be ‘engineered’ in arbitrary molecular systems if a single localised orbital – that diabatically follows nuclear displacements – is ionised. Specifically, we describe the use of natural bonding orbi…
Curve crossing in a manifold of coupled electronic states: direct quantum dynamics simulations of formamide Open
Fully quantum direct dynamics simulations generate the potential surface manifold for the photo-excited dynamics of small organic molecules.
Application of the unitary group approach to evaluate spin density for configuration interaction calculations in a basis of <i>S</i><sup>2</sup> eigenfunctions Open
We present an implementation of the spin‐dependent unitary group approach to calculate spin densities for configuration interaction calculations in a basis of spin symmetry‐adapted functions. Using S 2 eigenfunctions helps to reduce the si…
Electron Dynamics upon Ionization of Polyatomic Molecules: Coupling to Quantum Nuclear Motion and Decoherence Open
Knowledge about the electronic motion in molecules is essential for our understanding of chemical reactions and biological processes. The advent of attosecond techniques opens up the possibility to induce electronic motion, observe it in r…
Charge migration in polycyclic norbornadiene cations: Winning the race against decoherence Open
The observation of electronic motion remains a key target in the development of the field of attoscience. However, systems in which long-lived oscillatory charge migration may be observed must be selected carefully, particularly because it…
Direct methods for non-adiabatic dynamics: connecting the single-set variational multi-configuration Gaussian (vMCG) and Ehrenfest perspectives Open
In this article, we outline the current state-of-theart “on-the-fly” methods for non-adiabatic dynamics, highlighting the similarities and differences between them. We derive the equations of motion for both the Ehrenfest and variational m…
Publisher’s Note: “Nuclear spatial delocalization silences electron density oscillations in 2-phenyl-ethyl-amine (PEA) and 2-phenylethyl-N,N-dimethylamine (PENNA) cations” [J. Chem. Phys. 144, 104110 (2016)] Open
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Nuclear spatial delocalization silences electron density oscillations in 2-phenyl-ethyl-amine (PEA) and 2-phenylethyl-N,N-dimethylamine (PENNA) cations Open
We simulate electron dynamics following ionization in 2-phenyl-ethyl-amine and 2-phenylethyl-N,N-dimethylamine as examples of systems where 3 coupled cationic states are involved. We study two nuclear effects on electron dynamics: (i) coup…