
MORINI, Filippo; SHOJAEIKOHNEHSHAHRI, Reza; DELEUZE, Michael
The results of a yet to come experimental study of the electronic structure of biphenyl employing electron momentum spectroscopy (EMS) have been theoretically predicted, taking into account complications such as structural mobility in the electronic ground state, electronic correlation and relaxation, and a dispersion of the innervalence ionization intensity to electronically excited (shakeup) configurations in the cation. The main purpose of this work is to explore the current limits of EMS in unraveling details of the molecular structure, namely the torsional characteristics of large and floppy aromatic molecules. At the benchmark ADC(3)/ccpVDZ level of theory, the influence of the twist...

SHIROUDI, Abolfazl; DELEUZE, Michael
Reaction mechanisms for the initial stages of naphthalene oxidation at high temperatures (T> 600 K) have been studied theoretically using density functional theory along with various exchangecorrelation functionals, as well as the benchmark CBSQB3 quantum chemical approach. These stages correspond to the removal of hydrogen atoms by hydroxyl radical and the formation thereby of 1 and 2naphthyl radicals. The oxidation mechanisms of naphthalene by OH radicals under inert (He) conditions and at temperatures larger than 600 K have been studied using Density Functional Theory (DFT) along with various exchangecorrelation functionals. Comparison is made with benchmark CBSQB3 theoretical results. Kinetic rate...

SHIROUDI, Abolfazl; DELEUZE, Michael; Canneaux, Sébastien
The oxidation mechanisms of naphthalene by OH radicals under inert (He) conditions and at temperatures smaller than 410 K have been studied [1] using Density Functional Theory along with various exchangecorrelation functionals. Comparison is made with benchmark CBSQB3 theoretical results. Kinetic rate constants were estimated by means of Transition State Theory (TST) and statistical RiceRamspergerKasselMarcus (RRKM) theory. Effective rate constants have been calculated according to a steady state analysis using a twostep model. Comparison with experiment confirms that, on the OH addition reaction pathway leading to 1naphthol, the first bimolecular reaction step has an effective negative activation energy around 1.5...

SHIROUDI, Abolfazl; Deleuze, Michael S.; Canneaux, Sébastien
The oxidation mechanisms of naphthalene by OH radicals under inert (He)conditions have been studied using density functional theory along with various exchange−correlation functionals. Comparison has been made with benchmark CBSQB3 theoretical results. Kinetic rate constants were correspondingly estimated by means of transition
state theory and statistical Rice−Ramsperger−Kassel−Marcus (RRKM) theory. Comparison with experiment confirms that, on the OHaddition reaction pathway leading to 1naphthol, the first bimolecular reaction step has an effective negative activation energy around −1.5 kcal mol−1, whereas this step is characterized by an activation energy around 1 kcal mol−1 on the OHaddition reaction pathway leading to 2naphthol. Effective rate constants...


SHIROUDI, Abolfazl; Deleuze, Michael; MORINI, Filippo

SHIROUDI, Abolfazl; DELEUZE, Michael
Reaction mechanisms for the initial stages of naphthalene oxidation at high temperatures (T ≥ 600 K) have been studied theoretically using density functional theory along with various exchangecorrelation functionals, as well as the benchmark CBSQB3 quantum chemical approach. These stages correspond to the removal of hydrogen atoms by hydroxyl radical and the formation thereby of 1 and 2naphthyl radicals. Bimolecular kinetic rate constants were estimated by means of transition state theory. The excellent agreement with the available experimental kinetic rate constants demonstrates that a two step reaction scheme prevails. Comparison with results obtained with density functional theory in conjunction with...

Shojaei, S.H.Reza; MORINI, Filippo; Deleuze, M. S.
A comprehensive study of the He (I) ultraviolet photoelectron spectra of fluorene, carbazole and dibenzofuran is presented with the aid of oneparticle Green???s Function calculations employing the outervalence Green???s Function (OVGF) approach and the thirdorder algebraic diagrammatic construction [ADC(3)] scheme, along with Dunning???s correlation consistent basis sets of double and triple zeta quality (ccpVDZ, ccpVTZ). Extrapolations of the ADC(3) results for the outermost oneelectron pionization energies to the ccpVTZ basis set enable theoretical insights into He (I) measurements within 0.15 eV accuracy, up to the rionization onset. The lower ionization energy of carbazole is the combined result of mesomeric and...

Shojaei, S.H.Reza; MORINI, Filippo; Deleuze, M. S.

Shojaei, S.H.Reza; Vandenbussche, Jelle; Deleuze, M. S.; Bultinck, Patrick
The results of experimental studies of the valence electronic structure of 1butene by means of electron momentum spectroscopy (EMS) have been reinterpreted on the basis of molecular dynamical simulations in conjunction with the classical MM3 force field.
The computed atomic trajectories demonstrate the importance of
thermally induced nuclear dynamics in the electronic neutral ground
state, in the form of significant deviations from stationary points on the potential energy surface and considerable variations of the C???C???C???C dihedral angle. These motions are found to have a considerable
influence on the computed spectral bands and outervalence electron
momentum distributions. Euclidean distances between spherically
averaged electron momentum densities confirm that...

André, Thierry; MORINI, Filippo; Karamitros, M.; Delorme, R.; Le Loirec, C.; Campos, L.; Champion, C.; Groetz, J.E.; Fromm, M.; Bordage, M.C.; Perrot, Y.; Barberet, Ph.; Bernal, M.A.; Brown, J.M.C.; Deleuze, M. S.; Francis, Z.; Ivanchenko, V.; Mascialino, B.; Zacharatou, C.; Bardiès, M.; Incerti, S.
Monte Carlo simulations of Svalues have been carried out with the Geant4DNA extension of the Geant4 toolkit. The Svalues have been simulated for monoenergetic electrons with energies ranging from 0.1 keV up to 20 keV, in liquid water spheres (for four radii, chosen between 10 nm and 1 μm), and for electrons emitted by five isotopes of iodine (131, 132, 133, 134 and 135), in liquid water spheres of varying radius (from 15 μm up to 250 μm). The results have been compared to those obtained from other Monte Carlo codes and from other published data. The use of the...

Champagne, Benoit; DELEUZE, Michael; De Proft, Frank; Leyssens, Tom
Chemistry, Physical

DELEUZE, Michael; HUZAK, Matija; HAJGATO, Balazs
In this work we discuss in some computational and analytical details the issue of halfmetallicity in zigzag graphene nanoribbons and nanoislands of finite width, i.e. the coexistence of metallic nature for electrons with one spin orientation and insulating nature for the electrons of opposite spin, which has been recently predicted from socalled firstprinciple calculations employing Density Functional Theory. It is mathematically demonstrated and computationally verified that, within the framework of nonrelativistic and timeindependent quantum mechanics, like the sizeextensive spincontamination to which it relates, halfmetallicity is nothing else than a methodological artefact, due to a too approximate treatment of electron correlation...

SHOJAEIKOHNEHSHAHRI, Reza; MORINI, Filippo; DELEUZE, Michael
A comprehensive study of the He (I) ultraviolet photoelectron spectra of fluorene, carbazole and dibenzofuran is presented with the aid of oneparticle Green's Function calculations employing the outervalence Green's Function (OVGF) approach and the thirdorder algebraic diagrammatic construction [ADC(3)] scheme, along with Dunning's correlation consistent basis sets of double and triple zeta quality (ccpVDZ, ccpVTZ). Extrapolations of the ADC(3) results for the outermost oneelectron piionization energies to the ccpVTZ basis set enable theoretical insights into He (I) measurements within similar to 0.15 eV accuracy, up to the sigmaionization onset. The lower ionization energy of carbazole is the combined result of...

Shojaei, S.H.Reza; Morini, Filippo; Deleuze, Michael S.
The results of experimental studies of the valence
electronic structure of tetrahydrofuran employing He I photo
electron spectroscopy as well as Electron Momentum Spectrosco
py (EMS) have been reinterpreted on the basis of Molecular
Dynamical simulations employing the classical MM3 force ???eld
and largescale quantum mechanical simulations employing Born???
Oppenheimer Molecular Dynamics in conjunction with the
dispersion corrected ??B97XD exchangecorrelation functional.
Analysis of the produced atomic trajectories demonstrates the
importance of thermal deviations from the lowest energy path for
pseudorotation, in the form of considerable variations of the ring
puckering amplitude. These deviations are found to have a
signi???cant in???uence on several outervalence electron momentum
distributions, as well as on the He I...

Huzak, M.; Deleuze, M. S.
By applying the principles of a focal point analysis to finite field calculations, the static electric dipole polarizabilities of naphthalene, anthracene, and tetracene have been estimated up to the level of coupled cluster theory including single, double, and perturbative triple excitations in the limit of an asymptotically complete basis set. Thermal corrections to polarizabilities have been empirically estimated according to BornOppenheimer molecular dynamical simulations at 298 K employing density functional theory. Confrontation with the latest experimental values for isotropic polarizabilities ultimately indicates relative accuracies of the order of 1.2% (for naphthalene) to 3.5% (for anthracene), provided diffuse functions are incorporated...

HAJGATO, Balazs; DELEUZE, Michael
Nonlocal MP2like electron correlation in DFT calculations employing the double hybrid dispersion corrected B2PLYD functional is found to systematically quench antiferromagnetism in a variety of hexagonal graphene nanoflakes. The scaling in size of the associated spin contamination demonstrates further the artefactual character of any spinpolarization of electron densities in singlet electronic states.

HUZAK, Matija; HAJGATO, Balazs; DELEUZE, Michael
The vertical and adiabatic singlettriplet energy gaps, electron affinities and ionization energies of azulene, phenanthrene, pyrene, chrysene, and perylene are computed by applying the principles of a focal point analysis onto a series of singlepoint calculations at the level of HartreeFock theory, second, third, and fourthorder MollerPlesset perturbation theory, as well as coupled cluster theory including single, double and perturbative triple excitations, in conjunction with correlation consistent basis sets of improving quality. Results are supplemented with an extrapolation to the limit of an asymptotically complete basis set. According to our best estimates, azulene, phenanthrene, pyrene, chrysene, and perylene exhibit adiabatic...

Hajgato, Balazs; Morini, Filippo; Deleuze, Michael
The main purpose of this work is to reinvestigate the influence of nuclear dynamics in the electronic ground state of group 6 metal hexacarbonyl compounds [W(CO)6, Cr(CO)6, Mo(CO)6] on electron momentum density profiles obtained from experimental orbital reconstructions employing Electron Momentum Spectroscopy. We call into questionthe view (Liu et al. in Chem Phys Lett 497:229, 2010) that thermally induced nuclear displacements associated with the first three triply degenerate 1T2g, 1T1u, and 1T2u vibrational eigenmodes can be large enough at or near room temperature (298–310K) to explain on their own the unexpectedly large electron densities inferred for the frontier orbitals of...

Knippenberg, Stefan; HAJGATO, Balazs
In line with a recent study of the electronic structure of the cage compound norbornane (J. Chem. Phys. 121 (2004), 10525:J. Phys. Chem. A 109 (2005), 4267), symmetry adapted cluster expansion configuration interaction (SACCI) general R calculations have been performed and compared with results obtained by the third order algebraic diagrammatic construction scheme [ADC(3)]. Comparison has been made with previously performed electron momentum spectroscopy (EMS) and ultraviolet photoelectron measurements. The region around similar to 25eV (band 12), characterized by an elaborated band in the EMS spectrum which is missing in previous Green's function and ADC calculations, is investigated. This study...