1,721,016 research outputs found
The molecular electric quadrupole moment and electric-field-gradient induced birefringence (Buckingham effect) of Cl2
No full textAn ab initio investigation of the molecular properties rationalizing the electric-field-gradient induced birefringence
(Buckingham effect) for Cl2 is presented. The quadrupole moment is determined using hierarchies of basis sets and wavefunction
models. The electric dipole polarizability, the dipole – dipole – quadrupole and dipole – dipole – magnetic dipole
hyperpolarizabilities are determined exploiting a Coupled Cluster Singles and Doubles (CCSD) response approach. The properties
are zero-point vibrationally averaged, and the contribution of excited ro-vibrational states accounted for. To this end, the
interatomic 1Σ+g ground state potential has been computed at CCSD plus perturbative triples – CCSD(T) – level employing a
large augmented correlation consistent basis set. The effect of relativity is estimated at the Dirac-Hartree-Fock level. Our best
value for the quadrupole moment of Cl2 is (2.327 ± 0.010) au and it is in excellent agreement with experiment which, after
revision and dependent on the procedure employed for correcting the original estimate of (2.24 ± 0.04) au of Graham et al.,
[Mol. Phys., 93, 49, (1998)], ranges from (2.31 ± 0.04) au to (2.36 ± 0.04) au
From pentalene to dicyclopenta[b,g]naphthalene, or the change towards delocalized structures
No full textUsing triples-corrected coupled-cluster methods as well as other high-level theoretical approximations, the optimized parameters and isomerization barriers of the family of compounds cyclopentodiene-(benzene)(x)-cyclopentadiene (x = 0, 1, 2) are computed. In contrast to previous studies, s-indacene presents a localized C-2h geometry. Also, the localized structure of pentalene is found to be the most stable, but when two benzene rings are intercalated between the five-member rings of pentalene, the resulting molecule preferably adopts a delocalized D-2h conformation
(Damped) Response Methods for x-ray absorption spectroscopy, photoionization cross sections and other “exotic” molecular spectroscopies
No full textAn account of recent work on damped response methodologies based on either coupled cluster wave function ansatzes or time-dependent density functional theory to compute x-ray Near-Edge Absorption Fine Structures [1,2,3], photoionization cross-sections [5] as well as other “exotic” response properties of atoms and molecules in resonant and non-resonant frequency regions [3,4,6,7] will be presented.
References
[1] S. Coriani, O. Christiansen, T. Fransson, P. Norman, Phys. Rev. A 85, 022507 (2012)
[2] S. Coriani, T. Fransson, O. Christiansen, P. Norman J. Chem. Theory Comp. 8, 1616 (2012)
[3] T. Fransson, S. Coriani, O. Christiansen, P. Norman, J. Chem. Phys., 138, 124311 (2013)
[4] J. Kauczor, P. Norman, O. Christiansen, S. Coriani, to be submitted.
[5] J. Cukras, S. Coriani, P. Decleva, O. Christiansen, P. Norman, submitted to J. Chem. Phys.
[6] J. Cukras, S. Coriani, J. Kauczor, P. Norman, A. Rizzo, to be submitted
[7] T. Fahleson, J. Kauczor, P. Norman and S. Coriani. Mol. Phys. (2013), DOI:10.1080/00268976.2013.77939
Playing with Response
No full textResponse theory is a powerful and versatile theoretical framework for determining
molecular properties and spectra by probing the response to weak (external or
internal) electromagnetic fields. It provides efficient computational formulas for both
linear and nonlinear response properties, thus describing a plethora of effects. Rooted
on recent theoretical developments within the coupled-cluster ansatz and density
functional theory, in particular the so-called “damped” formulation of response
theory, I will present results for both “traditional” and new “perspective”
spectroscopies related to the absorption of light by the sample in presence of
external1,2 or internal magnetic fields,3 in the highly energetic x-ray frequency
region,4,5 and for photo-ionisation6 and photodetachment processes. 7
REFERENCES
1. F. Santoro, R. Improta, T. Fahleson, J. Kauczor, P. Norman, and S. Coriani, J.
Phys. Chem. Lett. 5 (2014) 1806
2. J. Cukras, J. Kauczor, P. Norman, A. Rizzo, G. Rikken, and S. Coriani, in
preparation.
3. J. Vaara, A. Rizzo, J. Kauczor, P. Norman, and S. Coriani, J. Chem. Phys. 140
(2014) 134103
4. J. Kauczor, P. Norman, O. Christiansen, and S. Coriani, J. Chem. Phys. 139
(2013) 211102
5. T Fransson, S. Coriani, O. Christiansen, and P. Norman J. Chem. Phys. 138
(2013) 124311
6. N. H. List, S. Coriani, J. Kongsted, and O. Christiansen, submitted to J. Chem.
Phys.
7. J. Cukras, P. Decleva, and S. Coriani. J. Chem. Phys., under revision
8. J. Cukras, S. Coriani, P. Decleva, O. Christiansen, and P. Norman J. Chem. Phys.
139 (2013) 09410
Correlated Response Methods to model absorption, ionization and scattering phenomena
No full textAn overview of our recent work on the extension of Linear Coupled Cluster
Response Theory to compute Near-Edge Absorption Fine Structures [1,2,3],
photoionization cross-sections [5] as well as other linear response properties of
atoms and molecules in resonant frequency regions [3,4] will be presented.
[1] S. Coriani, O. Christiansen, T. Fransson, P. Norman, Phys. Rev. A 2012,
85, 022507
[2] S. Coriani, T. Fransson, O. Christiansen, P. Norman J. Chem. Theory
Comp. 2012, 8, 1616
[3] T. Fransson, S. Coriani, O. Christiansen, P. Norman, Submitted to J. Chem.
Phys.
[4] S. Coriani, J. Kauczor, P. Norman, O. Christiansen, to be submitted
[5] J. Cukras, S. Coriani, P. Decleva, O. Christiansen, P. Norman, , to be
submitted
First-order properties and Buckingham birefringence of N2O and OCS – A computational (re)investigation
No full textPrompted by recent experimental reinvestigations of the Buckingham birefringence of CO, CO2, OCS and N2O, we have carried out our own reinvestigation of the relevant first- and second-order properties entering the electric-field-gradient-induced birefringence effect of N2O and OCS by means of state-of-the-art quantum chemical methods. The computed and experimentally derived results remain at significant variance, also in consequence of a remarkable disagreement between the ab initio and the experimental values of the quadrupole moment relative to the centre of the nuclear masses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Response methods for light-matter interactions: old and new spectroscopies and challenging effects
No full textResponse theory constitutes a powerful and versatile theoretical framework for determining molecular properties and spectra by probing the response to weak (external or internal) electromagnetic fields. It provides efficient computational formulas for both linear and nonlinear response properties, thus describing a plethora of optical effects. Rooted on recent theoretical developments within the coupled-cluster ansatz and density functional theory, in particular the so-called “damped” formulation of response theory, aka complex polarization propagator, we present results for both “traditional” and new “perspective” spectroscopies related to the absorption of light by the sample in presence external1,2 or internal magnetic fields,3 in the highly energetic x-ray frequency region,4,5 and for photo-ionisation6 and photodetachment processes. 7
REFERENCES
1. F. Santoro, R. Improta, T. Fahleson, J. Kauczor, P. Norman, and S. Coriani, J. Phys. Chem. Lett. 5 (2014) 1806
2. J. Cukras, J. Kauczor, P. Norman, A. Rizzo, G. Rikken, and S. Coriani, in preparation.
3. J. Vaara, A. Rizzo, J. Kauczor, P. Norman, and S. Coriani, J. Chem. Phys. 140 (2014) 134103
4. J. Kauczor, P. Norman, O. Christiansen, and S. Coriani, J. Chem. Phys. 139 (2013) 211102
5. T Fransson, S. Coriani, O. Christiansen, and P. Norman J. Chem. Phys. 138 (2013) 124311
6. J. Cukras, P. Decleva, and S. Coriani. J. Chem. Phys., under revision
7. J. Cukras, S. Coriani, P. Decleva, O. Christiansen, and P. Norman J. Chem. Phys. 139 (2013) 09410
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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