Imperial College London

ProfessorMichaelBearpark

Faculty of Natural SciencesDepartment of Chemistry

Professor of Computational Chemistry
 
 
 
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Contact

 

+44 (0)20 7594 5727m.bearpark

 
 
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Location

 

110AMolecular Sciences Research HubWhite City Campus

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Summary

 

Publications

Publication Type
Year
to

142 results found

Segarra-Martí J, Nouri SM, Bearpark MJ, 2021, Modelling Photoionisations in Tautomeric DNA Nucleobase Derivatives 7H-Adenine and 7H-Guanine: Ultrafast Decay and Photostability, Photochem, Vol: 1, Pages: 287-301

<jats:p>The study of radiation effects in DNA is a multidisciplinary endeavour, connecting the physical, chemical and biological sciences. Despite being mostly filtered by the ozone layer, sunlight radiation is still expected to (photo)ionise DNA in sizeable yields, triggering an electron removal process and the formation of potentially reactive cationic species. In this manuscript, photoionisation decay channels of important DNA tautomeric derivatives, 7H-adenine and 7H-guanine, are characterised with accurate CASSCF/XMS-CASPT2 theoretical methods. These simulation techniques place the onset of ionisation for 7H-adenine and 7H-guanine on average at 8.98 and 8.43 eV, in line with recorded experimental evidence when available. Cationic excited state decays are analysed next, uncovering effective barrierless deactivation routes for both species that are expected to decay to their (cationic) ground state on ultrafast timescales. Conical intersection topographies reveal that these photoionisation processes are facilitated by sloped single-path crossings, known to foster photostability, and which are predicted to enable the (VUV) photo-protection mechanisms present in these DNA tautomeric species.</jats:p>

Journal article

Segarra-Martí J, Bearpark MJ, 2021, Modelling photoionisation in isocytosine: potential formation of longer-lived excited state cations in its keto form., ChemPhysChem: a European journal of chemical physics and physical chemistry, ISSN: 1439-4235

Studying the effects of UV and VUV radiation on non-canonical DNA/RNA nucleobases allows us to compare how they release excess energy following absorption with respect to their canonical counterparts. This has attracted much research attention in recent years because of its likely influence on the origin of our genetic lexicon in prebiotic times. Here we present a CASSCF and XMS-CASPT2 theoretical study of the photoionisation of non-canonical pyrimidine nucleobase isocytosine in both its keto and enol tautomeric forms. We analyse their lowest energy cationic excited states including 2 π + , 2 n O +  and 2 n N +  and compare these to the corresponding electronic states in cytosine. Investigating lower-energy decay pathways we find - unexpectedly - that keto-isocytosine + presents a sizeable energy barrier potentially inhibiting decay to its cationic ground state, whereas enol-isocytosine + features a barrierless and consequently ultrafast pathway analogous to the one previously found for the canonical (keto) form of cytosine + . Dynamic electron correlation reduces the energy barrier in the keto form substantially (by ~1 eV) but it is nevertheless still present. We additionally compute UV/Vis absorption signals of the structures encountered along these decay channels to provide spectroscopic fingerprints to assist future experiments in monitoring these intricate photo-processes.

Journal article

Fare C, Yuan L, Cordon-Preciado V, Michels JJ, Bearpark MJ, Rich PR, van Thor JJet al., 2020, A radical-triggered reaction mechanism of the green-to-red photoconversion of EosFP, The Journal of Physical Chemistry B, Vol: 124, Pages: 7765-7778, ISSN: 1520-6106

Reaction intermediates in the green-to-red photoconversion of the photochromic fluorescent protein EosFP have been observed using high-intensity continuous blue illumination. An intermediate was identified through light induced accumulation that continues to convert the green form in subsequent darkness, putatively containing a tyrosyl radical, albeit with anomalously shifted features in both electronic and FTIR spectra. Lowering the pH to 5.5 significantly delays the decay of this tyrosyl intermediate, which is accompanied by Stark-shifted features in the electronic spectra of reactants and products. Vibrational mode assignments for the high frequency and fingerprint FTIR spectral regions of reaction intermediates support a proposed sequence of events where the newly formed Cα=Cβ ethylenic bond precedes modifications on the His62 imidazole ring and confirms a C=O(NH2) product group on Phe61. We propose a reaction mechanism that involves tyrosyl generation via singlet excited state mediated oxidation which subsequently triggers the covalent reactions by oxidation of the green chromophore.

Journal article

Segarra-Martí J, Segatta F, Mackenzie TA, Nenov A, Rivalta I, Bearpark M, Garavelli Met al., 2020, Modeling multidimensional spectral lineshapes from first principles: Application to water-solvated adenine, Faraday Discussions, Vol: 221, Pages: 219-244, ISSN: 1359-6640

In this discussion we present a methodology to describe spectral lineshape from first principles, providing insight into the solvent-solute molecular interactions in terms of static and dynamic disorder and how these shape the signals recorded experimentally in linear and nonlinear optical spectroscopies, including two-dimensional electronic spectroscopy (2DES). Two different strategies for simulating the lineshape are compared, in which both the coupling to the intra-molecular vibrations and the influence exerted by the different water distributions attained along a molecular dynamics (MD) simulation are accurately described. The first method accounts for such water arrangements as first order perturbations on the adenine energies computed for a single reference (gas phase) quantum calculation. The second method requires to compute the manifold of excited states explicitly at each simulation snapshot, employing a hybrid quantum mechanics/molecular mechanics (QM/MM) scheme. Both approaches are applied to a large number of states of the adenine singlet excited manifold (chosen because of its biological role), and compared with available experimental data. They give comparable results but the first approach is two orders of magnitude faster. We show how the various contributions (static/dynamic disorder, intra-/inter-molecular interactions) sum up to build the total broadening observed in experiments.

Journal article

Segarra-Marti J, Tran T, Bearpark M, 2019, Computing the ultrafast and radiationless electronic excited state decay of cytosine and 5‐methyl‐cytosine cations: uncovering the role of dynamic electron correlation, ChemPhotoChem, Vol: 3, Pages: 856-865, ISSN: 2367-0932

Photoionisation in DNA, i.e. the process of photoinduced electron removal from the chromophoric species − the nucleobases − leading to their cationic form, has been scarcely studied despite being considered to be responsible for significant damaging instances in our genetic material. In this contribution we theoretically characterise the electronic ground and excited state decay pathways of cationic DNA nucleobase cytosine+ and its epigenetic derivative 5‐methyl‐cytosine+, including the effects of dynamic electron correlation on energies and geometries of minima and conical intersections. We do this by comparing the results of XMS‐CASPT2 calculations with CASSCF estimates and we find some significant differences between the results of these two methods. In particular, including dynamic electron correlation is found to significantly reduce the barrier to access the (D1/D0) conical intersection. We find notable similarities in both cytosine and 5‐methyl‐cytosine cations, accessible conical intersections in the vicinity of the Franck‐Condon region are found. This points towards an ultrafast depopulation of their electronic excited states. Moreover, the shape of the ground state potential energy surface strongly directs the decaying excited state population towards the cationic ground state minimum on ultrafast timescales, preventing photofragmentation and thus explaining their photostability.

Journal article

Tran T, Segarra-Martí J, Bearpark M, Robb MAet al., 2019, Molecular vertical excitation energies studied with first-order RASSCF (RAS[1,1]): balancing covalent and ionic excited states, Journal of Physical Chemistry A, Vol: 123, Pages: 5223-5230, ISSN: 1089-5639

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 results of Thiel, were obtained using a RASSCF space that contains at most one hole and one particle in the RAS1 and RAS3 spaces, respectively, which we denote as RAS[1,1]. This subset of configurations recovers mainly the effect of polarization and semi-internal electronic correlation that is only included in CASSCF in an averaged way. Adding all-external correlation by allowing double excitations from RAS1 and RAS2 into RAS3 did not improve the results, and indeed, they were slightly worse. The accuracy of the first-order RASSCF computations is demonstrated to be a function of whether the state of interest can be classified as covalent or ionic in the space of configurations built from orbitals localized onto atomic sites. For covalent states, polarization and semi-internal correlation effects are negligible (RAS[1,1]), while for ionic states, these effects are large (because of inherent diffusiveness of these states compared to the covalent states) and, thus, an acceptable agreement with MS-CASPT2 can be obtained using first-order RASSCF with the extra basis set involving 3p orbitals in most cases. However, for those ionic states that are quasi-degenerate with a Rydberg state or for nonlocal nπ* states, there remains a significant error resulting from all external correlation effects.

Journal article

Segarra-Martí J, Tran T, Bearpark MJ, 2019, Ultrafast and radiationless electronic excited state decay of uracil and thymine cations: computing the effects of dynamic electron correlation, Physical Chemistry Chemical Physics, Vol: 21, Pages: 14322-14330, ISSN: 1463-9076

In this article we characterise the radiationless decay of the first few electronic excited states of the cations of DNA/RNA nucleobases uracil and thymine, including the effects of dynamic electron correlation on energies and geometries (optimised with XMS-CASPT2). In both systems, we find that one state of 2n+O and another two of 2π+ character can be populated following photoionisation, and their different minima and interstate crossings are located. We find strong similarities between uracil and thymine cations: with accessible conical intersections suggesting that depopulation of their electronic excited states takes place on ultrafast timescales in both systems, suggesting that they are photostable in agreement with previous theoretical (uracil+) evidence. We find that dynamic electron correlation separates the energy levels of the "3-state" conical intersection (D2/D1/D0)CI previously located with CASSCF for uracil+, which will therefore have a different geometry and higher energy. Simulating the electronic and vibrational absorptions allows us to characterise spectral fingerprints that could be used to monitor these cation photo-processes experimentally.

Journal article

Polyak I, Bearpark MJ, Robb MA, 2018, Application of the unitary group approach (UGA) to evaluate spindensity for Configuration Interaction (CI) calculations in a basisof S$^{2}$ eigenfunctions, International Journal of Quantum Chemistry, Vol: 118, ISSN: 0020-7608

We present an implementation of the spin-dependent unitary group approachto calculate spin densities for CI calculations in a basis of spinsymmetry-adapted functions. Using S$^{2}$ eigenfunctions helps toreduce the size of configuration space and is beneficial in studiesof the systems where selection of states of specific spin symmetryis crucial. In order to achieve this, we combine the method to calculate$U(n)$ generator matrix elements developed by Robb and Downward~[\onlinecite{downward_1977}]with the approach of Gould and Battle to calculate $U(2n)$ generatormatrix elements~[\onlinecite{battle_1993}]. We also compareand contrast the spin density formulated in terms of the spin-independentunitary generators arising from the group theory formalism and equivalent formulation of the spin density representation in terms of the one- and two-electron charge densities.

Journal article

Polyak I, Jenkins A, Vacher M, Bouduban M, Bearpark M, Robb MAet al., 2018, Charge migration engineered by localisation: electron-nuclear dynamics in polyenes and glycine, Molecular Physics, Vol: 116, Pages: 2474-2489, ISSN: 0026-8976

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 orbitals in Complete Active Space Configuration Interaction (CASCI) calculations to form cationic states with localised charge, providing consistently well-defined initial conditions across a zero point energy vibrational ensemble of molecular geometries. In Ehrenfest dynamics simulations following localised ionisation of -electrons in model polyenes (hexatriene and decapentaene) and -electrons in glycine, oscillatory charge migration can be observed for several femtoseconds before dephasing. Including nuclear motion leads to slower dephasing compared to fixed-geometry electron-only dynamics results. For future work, we discuss the possibility of designing laser pulses that would lead to charge migration that is experimentally observable, based on the proposed diabatic orbital approach.

Journal article

Vacher M, Bearpark M, Robb MA, Malhado JPet al., 2017, Electron dynamics upon ionisation of polyatomic molecules: Coupling to quantum nuclear motion and decoherence, Physical Review Letters, Vol: 118, Pages: 1-5, ISSN: 1079-7114

Knowledge about the electronic motion in molecules is essential for our understanding of chemicalreactions and biological processes. The advent of attosecond techniques opens up the possibility toinduce electronic motion, observe it in real time and potentially steer it. A fundamental questionremains the factors influencing electronic decoherence and the role played by nuclear motion in thisprocess. Here, we simulate the dynamics upon ionisation of the polyatomic molecules para-xyleneand modified bismethylene-adamantane, with a quantum mechanical treatment of both electron andnuclear dynamics using the direct dynamics variational multi-configuration Gaussian method. Oursimulations give new important physical insights about the expected decoherence process. We haveshown that the decoherence of electron dynamics happens on the time scale of a few femtoseconds,with the interplay of different mechanisms: thedephasingis responsible for the fast decoherencewhile thenuclear overlap decaymay actually help maintaining it and is responsible for small revivals.

Journal article

Spinlove KE, Vacher M, Bearpark M, Robb MA, Worth GAet al., 2017, Using quantum dynamics simulations to follow the competition between charge migration and charge transfer in polyatomic molecules, CHEMICAL PHYSICS, Vol: 482, Pages: 52-63, ISSN: 0301-0104

Journal article

Robb MA, 2016, Charge migration in polycyclic norbornadiene cations: winning the race against decoherence, Journal of Chemical Physics, Vol: 145, ISSN: 1089-7690

The observation of electronic motion remains a key target in the development of the eld of attoscience.However, systems in which long-lived oscillatory charge migration may be observed must be selected carefully,particularly because it has been shown that nuclear spatial delocalization leads to a loss of coherent electrondensity oscillations. Here we demonstrate electron dynamics in norbornadiene and extended systems wherethe hole density migrates between two identical chromophores. By studying the e ect of nuclear motionand delocalization in these example systems, we present the physical properties that must be considered incandidate molecules in which to observe electron dynamics. Furthermore, we also show a key contribution tonuclear delocalization arises from motion in the branching plane of the cation. For the systems studied, thedephasing time increases with system size while the energy gap between states, and therefore the frequency ofthe density oscillation, decreases with size (obeying a simple exponential dependence on the inter-chromophoredistance). We present a system that balances these two e ects and shows several complete oscillations in thespin density before dephasing occurs.

Journal article

Abdullahi MH, Thompson LM, Bearpark MJ, Vinader V, Afarinkia Ket al., 2016, The role of substituents in retro Diels-Alder extrusion of CO2 from 2(H)-pyrone cycloadducts, Tetrahedron, Vol: 72, Pages: 6021-6024, ISSN: 1464-5416

An experimental and computational investigation is conducted into the role of substituents in retro Diels–Alder extrusion of CO2 from 2-oxa-bicyclo[2.2.2]oct-5-en-3-ones. We provide the first experimental evidence that loss of CO2 from the cycloadducts significantly depends on the nature and position of the substituents. For example, we show that whilst 5-carboethoxy-2-pyrone undergoes a more facile cycloaddition that 3-carboethoxy-2-pyrone, the cycloadduct from the latter pyrone undergoes a more facile loss of CO2 than the cycloadduct from the former pyrone.

Journal article

Vacher M, Bearpark MJ, Robb MA, 2016, Direct methods for non-adiabatic dynamics: connecting the single-set variational multi-confguration Gaussian (vMCG) and Ehrenfest perspectives, Theoretical Chemistry Accounts, Vol: 135, ISSN: 1432-881X

In this article, we outline the current state-of-theart“on-the-fly” methods for non-adiabatic dynamics, highlightingthe similarities and differences between them. Wederive the equations of motion for both the Ehrenfest andvariational multi-configuration Gaussian (vMCG) methodsfrom the Dirac–Frenkel variational principle. We explorethe connections between these two methods by presentingan alternative derivation of the vMCG method, which givesthe Ehrenfest equations of motion when taking the appropriatelimits.

Journal article

Casellas J, Bearpark MJ, Reguero M, 2016, Excited-State Decay in the Photoisomerisation of Azobenzene: A New Balance between Mechanisms, Chemphyschem, Vol: 17, Pages: 3068-3079, ISSN: 1439-7641

The mechanism of the photoisomerization of azobenzene has been studied by means of multiconfigurational ab initio calculations. Our results show that it is necessary to account for the dynamic electron correlation in the location of the critical points (CASPT2 optimizations) to obtain a correct description of the topography of the potential energy surfaces of the low-energy singlet excited states. Using this methodology, we have found that the state populated by the initial excitation is the S2 (ππ*) state, which decays very efficiently to the S1 (nπ*) state at a pedal-like non-rotated geometry. On the S1 state, relaxation leads to a rotated geometry where the system decays to the ground state, in which further relaxation can lead to either the trans or cis geometries. However the S1/S0 CI seam also extends to planar geometries, so this reaction path is also accessible for rotation-constrained systems. Our results explain the experimental observations satisfactorily.

Journal article

Vacher M, Albertani FEA, Jenkins AJ, Polyak I, Bearpark M, Robb MAet al., 2016, Electron and nuclear dynamics following ionisation of modified bismethylene-adamantane, Faraday Discussions, Vol: 194, Pages: 95-115, ISSN: 1364-5498

We have simulated the coupled electron and nuclear dynamics using the Ehrenfest method upon valence ionisation of modified bismethylene-adamantane (BMA) molecules where there is an electron transfer between the two π bonds. We have shown that the nuclear motion significantly affects the electron dynamics after a few fs when the electronic states involved are close in energy. We have also demonstrated how the non-stationary electronic wave packet determines the nuclear motion, more precisely the asymmetric stretching of the two π bonds, illustrating “charge-directed reactivity”. Taking into account the nuclear wave packet width results in the dephasing of electron dynamics with a half-life of 8 fs; this eventually leads to the equal delocalisation of the hole density over the two methylene groups and thus symmetric bond lengths.

Journal article

Jenkins AJ, Vacher M, Bearpark MJ, Robb MAet al., 2016, Nuclear spatial delocalization silences electron density oscillations in 2-phenyl-ethyl-amine (PEA) and 2-phenylethyl-N,N-dimethylamine (PENNA) cations (vol 144, 104110, 2016), JOURNAL OF CHEMICAL PHYSICS, Vol: 144, ISSN: 0021-9606

Journal article

Jenkins AJ, Vacher M, Bearpark MJ, Robb MAet al., 2016, Nuclear spatial delocalization silences electron density oscillations in 2-phenyl-ethyl-amine (PEA) and 2-phenylethyl-N,N-dimethylamine (PENNA) cations, Journal of Chemical Physics, Vol: 144, ISSN: 1089-7690

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) coupled electron-nuclear motion and (ii) nuclear spatial delocalization as a result of the zero-point energy in the neutral molecule. Within the Ehrenfest approximation, our calculations show that the coherent electron dynamics in these molecules is not lost as a result of coupled electron-nuclear motion. In contrast, as a result of nuclear spatial delocalization, dephasing of the oscillations occurs on a time scale of only a few fs, long before any significant nuclear motion can occur. The results have been rationalized using a semi-quantitative model based upon the gradients of the potential energy surfaces.

Journal article

Vigor WA, Spencer JS, Bearpark MJ, Thom AJWet al., 2016, Understanding and improving the efficiency of full configuration interaction quantum Monte Carlo, JOURNAL OF CHEMICAL PHYSICS, Vol: 144, ISSN: 0021-9606

Journal article

McArdle I, Fare C, Bearpark M, Thomas G, Butcher S, Tomlinson C, Mueller M, Burbidge S, Lawlor S, Ferrer J, Rzepa H, Harvey M, Mclean A, Mason Net al., 2015, Research Data Management 'Green Shoots' Pilot Programme, Final Reports, Research Data Management 'Green Shoots' Pilot Programme, Final Reports

This document contains the final reports of six Research Data Management "Green Shoots" projects run at Imperial College in 2014.

Report

Sanchez-Gonzalez A, Barillot TR, Squibb RJ, Kolorenc P, Agaker M, Averbukh V, Bearpark MJ, Bostedt C, Bozek JD, Bruce S, Montero SC, Coffee RN, Cooper B, Cryan JP, Dong M, Eland JHD, Fang L, Fukuzawa H, Guehr M, Ilchen M, Johnsson AS, Liekhus-S C, Marinelli A, Maxwell T, Motomura K, Mucke M, Natan A, Osipov T, Ostlin C, Pernpointner M, Petrovic VS, Robb MA, Sathe C, Simpson ER, Underwood JG, Vacher M, Walke DJ, Wolf TJA, Zhaunerchyk V, Rubensson J-E, Berrah N, Bucksbaum PH, Ueda K, Feifel R, Frasinski LJ, Marangos JPet al., 2015, Auger electron and photoabsorption spectra of glycine in the vicinity of the oxygen K-edge measured with an X-FEL, JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS, Vol: 48, ISSN: 0953-4075

Journal article

Vacher M, Steinberg L, Jenkins AJ, Bearpark MJ, Robb MAet al., 2015, Electron dynamics following photoionization: decoherence due to the nuclear-wave-packet width, Physical Review A, Vol: 92, Pages: 1-6, ISSN: 1094-1622

The advent of attosecond techniques opens up the possibility to observe experimentally electron dynamics following ionization of molecules. Theoretical studies of pure electron dynamics at single fixed nuclear geometries in molecules have demonstrated oscillatory charge migration at a well-defined frequency but often neglecting the natural width of the nuclear wave packet. The effect on electron dynamics of the spatial delocalization of the nuclei is an outstanding question. Here, we show how the inherent distribution of nuclear geometries leads to dephasing. Using a simple analytical model, we demonstrate that the conditions for a long-lived electronic coherence are a narrow nuclear wave packet and almost parallel potential-energy surfaces of the states involved. We demonstrate with numerical simulations the decoherence of electron dynamics for two real molecular systems (paraxylene and polycyclic norbornadiene), which exhibit different decoherence time scales. To represent the quantum distribution of geometries of the nuclear wave packet, the Wigner distribution function is used. The electron dynamics decoherence result has significant implications for the interpretation of attosecond spectroscopy experiments since one no longer expects long-lived oscillations.

Journal article

Santolini V, Malhado JP, Robb MA, Garavelli M, Bearpark MJet al., 2015, Photochemical reaction paths of cis-dienes studied with RASSCF: the changing balance between ionic and covalent excited states, Molecular Physics, Vol: 113, Pages: 1978-1990, ISSN: 1362-3028

The balanced description of ionic and covalent molecular excited electronic states still presents a challenge for currentelectronic structure methods. In this contribution, we show how the restricted active space self-consistent field (RASSCF)method can be used to address this problem, applied to two dienes in the cis conformation. As with the closely relatedcomplete active space self-consistent field (CASSCF) method, the construction of the orbital active space in the RASSCFmethodology requires the a priori formulation of a physical or theoretical model of the system being studied. In this article,we discuss how the active space can be constructed in a guided and systematic way, using pairs of natural bond orbitalsas correlating partner orbitals (oscillator orbitals) and semi-internal correlation. The resulting balanced description of thecovalent and ionic valence excited states – with the ionic state correctly lower in energy at the Franck–Condon geometry –is suitable to study the photochemistry of these and other molecules.

Journal article

Robb MA, Meisner J, Vacher M, Bearpark Met al., 2015, Geometric rotation of the nuclear gradient at a conical intersection: Extension to complex rotation of diabatic states, Journal of Chemical Theory and Computation, Vol: 11, Pages: 3115-3122, ISSN: 1549-9618

Nonadiabatic dynamics in the vicinity of conical intersections is of essential importance in photochemistry. It is well known that if the branching space is represented in polar coordinates, then for a geometry represented by angle θ, the corresponding adiabatic states are obtained from the diabatic states with the mixing angle θ/2. In an equivalent way, one can study the relation between the real rotation of diabatic states and the resulting nuclear gradient. In this work, we extend the concept to allow a complex rotation of diabatic states to form a nonstationary superposition of electronic states. Our main result is that this leads to an elliptical transformation of the effective potential energy surfaces; i.e., the magnitude of the initial nuclear gradient changes as well as its direction. We fully explore gradient changes that result from varying both θ and ϕ (the complex rotation angle) as a way of electronically controlling nuclear motion, through Ehrenfest dynamics simulations for benzene cation.

Journal article

Vacher M, Meisner J, Mendive-Tapia D, Bearpark MJ, Robb MAet al., 2015, Electronic Control of Initial Nuclear Dynamics Adjacent to a Conical Intersection, JOURNAL OF PHYSICAL CHEMISTRY A, Vol: 119, Pages: 5165-5172, ISSN: 1089-5639

Journal article

Vigor WA, Spencer JS, Bearpark MJ, Thom AJWet al., 2015, Minimising biases in full configuration interaction quantum Monte Carlo, Journal of Chemical Physics, Vol: 142, ISSN: 1089-7690

Journal article

Vacher M, Mendive-Tapia D, Bearpark MJ, Robb MAet al., 2015, Electron dynamics upon ionization: Control of the timescale through chemical substitution and effect of nuclear motion, Journal of Chemical Physics, Vol: 142, ISSN: 1089-7690

Journal article

Boggio-Pasqua M, Bearpark MJ, Rob MA, 2015, The Role of Extended Conical Intersection Seams in Photochromic Systems, International Conference of Computational Methods in Sciences and Engineering (ICCMSE), Publisher: AMER INST PHYSICS, Pages: 453-456, ISSN: 0094-243X

Conference paper

Malhado JP, Bearpark MJ, Hynes JT, 2014, Non-adiabatic dynamics close to conical intersections and the surface hopping perspective., Frontiers in Chemistry, Vol: 2, ISSN: 2296-2646

Conical intersections play a major role in the current understanding of electronic de-excitation in polyatomic molecules, and thus in the description of photochemistry and photophysics of molecular systems. This article reviews aspects of the basic theory underlying the description of non-adiabatic transitions at conical intersections, with particular emphasis on the important case when the dynamics of the nuclei are treated classically. Within this classical nuclear motion framework, the main aspects of the surface hopping methodology in the conical intersection context are presented. The emerging picture from this treatment is that of electronic transitions around conical intersections dominated by the interplay of the nuclear velocity and the derivative non-adiabatic coupling vector field.

Journal article

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