1,721,092 research outputs found
The calculation of molecular double ionization spectra by Green's functions
No full textThe Green’s function ADC(2) has long proved to be a successful method for the study of dense double ionization spectra of molecules and clusters. This paper focuses on the computational aspects of the method, illustrating in particular the algorithms it entails in the context of subspace iteration techniques to compute eigenvalues and eigenvectors, and how these can be efficiently implemented. It is shown that, as in direct-CI procedures, the key matrix-multiply operation is effectively reduced to a number of smaller cache-size oper- ations with matrix blocks built on-the-fly from the two-electron integrals, which can be implemented through fast basic linear algebra routines. Some parallelization aspects and specific diagonalization procedures are briefly discussed
A quantitative view of charge transfer in the hydrogen bond: the water dimer case
No full textThe hydrogen bond represents a fundamental intermolecular interaction that binds molecules in vapor and liquid water. A crucial and debated aspect of its electronic structure and chemistry is the charge transfer (CT) accompanying it. Much effort has been devoted, in particular, to the study of the smallest prototype system, the water dimer, but even here results and interpretations differ widely. In this paper, we reassess CT in the water dimer by using charge-displacement analysis. Besides a reliable estimate of the amount of CT (14.6 me) that characterizes the system, our study provides an unambiguous context, and very useful bounds, within which CT effects may be evaluated, crucially including the associated energy stabilization
On the Dewar-Chatt-Duncanson model for catalytic gold(I) complexes
No full textWe provide a rigorous model-free definition and a detailed theoretical analysis of the electron- charge displacements making up the donation and back-donation compo- nents of the Dewar–Chatt–Duncanson model in some realistic catalytic inter- mediates of formula L–AuI–S in which L is an N-heterocyclic carbene or Cl and S is an eta2-coordinated substrate containing a C C multiple bond. We thus show, contrary to a widely held view, that the gold substrate bond is characterized by a large p back-donation component that is comparable to, and often as large as, the s donation. The back-donation is found to be a highly tunable bond component and we analyze its relationship with the nature of the auxiliary ligand L and with structural (interdependent) factors such as metal–substrate bond lengths and carbon pyramidalization
Intermolecular Coulombic decay of molecular clusters: Identification of the decay mechanism using a new hole-population analysis
No full textSingly ionized states of molecular clusters with an inner-valence vacancy have recently been shown to undergo an efficient electronic decay. The mechanism of the decay, which is absent in the isolated molecules that build up the clusters, is proposed to be of intermolecular Coulombic nature. As explicit example to further investigate this new decay process, the valence ionization spectrum of the HF(H2O)2 cluster is computed with the ADC(3) one-particle Green's function method. In the inner-valence part of the spectrum, characteristic dense line bundles due to the ultrafast electronic decay of the corresponding cationic states are observed. A new hole-population analysis method for the very many computed cationic states is presented. This method allows for a quantitative measure and characterization of the hole localization pattern of the cationic states. The dense line bundles which mimic the continuous decay distributions in our finite basis set approach are analyzed in detail. The resulting intermolecular character of the states confirms the recently proposed intermolecular Coulombic mechanism for the electronic decay in molecular clusters. The decay leads to dicationic states with two vacancies located on neighboring monomer units
Valence hole localization in core-valence doubly ionized states of ionic molecules and its impact on KLV Auger spectroscopy
No full textThe complete spectra of core-valence dicationic states, i.e., states with one vacancy in the core and one in
the valence shell, of the molecules BF3, AlF3 , BCl3, and AlCl3, are investigated by the Green’s-function
method. An analysis of the double-hole density in the corresponding correlated states shows that when the core
hole is on a ligand ~halogen! atom, the valence hole is also strongly localized, either on the same ligand or on
a different ligand. As a result these states can be classified as either on-core or off-core site states. We discuss
how the localization phenomena are at the origin of the chlorine KLV Auger spectra of BCl3 and AlCl3 and,
in particular, how they provide a complete and conclusive interpretation of these spectra. Due to the intraatomic
nature of the Auger process, the simulation of the chlorine and aluminum KLV Auger spectra is done
by a simple convolution of the respective on-core site component of the computed two-hole density distribution.
The ligand atom spectra contain almost no information about the molecular system, representing an
indistinct self-image of the ligand atom itself, whereas the central atom spectra render a distinct foreign image
of the molecular environment
Double ionization of fluorinated benzenes: Hole localization and delocalization effects
No full textThe dense double ionization spectra of all the twelve fluoro-substituted benzene molecules are investigated in great detail by Green’s function ADC 2 calculations and a two-hole density mapping. Double ionization is shown to provide an extremely sensitive tool of electronic structure analysis. The calculations evidence and measure quantitatively how the charge distribution is dictated by the complex interplay between the resilience of the aromatic ring electronic structure and the disruptive effect of the electronegative halogen substituents. Successive substitutions are found not to have any synergic effect, but affect the spectra in very identifiable ways. The Auger spectra of the fluorobenzenes are interpreted in the light of the charge distribution results, using the foreign-imaging model. The double charge transfer spectra are also analyzed and discussed
Out-of-equilibrium quantum dynamics of fermionic gases in the presence of localized particle loss
Full text linkWe address the effects of dissipative defects giving rise to a localized
particle loss, in one-dimensional non-interacting lattice fermionic gases
confined within a region of size . We consider homogeneous systems within
hard walls and inhomogeneous systems where the particles are trapped by
space-dependent external potentials, such as harmonic traps. We model the
dissipative particle-decay mechanism by Lindblad master equations governing the
time evolution of the density matrix. The resulting quantum dynamics is
analyzed in protocols starting from the ground state of the Hamiltonian for
particles, then evolving under the effect of one dissipative
particle-loss defect, for example at the center of the system. We study the
interplay between time, size and the number of initial particles,
considering two different situations: (i) fixed number of initial
particles; (ii) fixed ratio , corresponding to the thermodynamic
limit of the initial equilibrium state. We show that the quantum evolutions of
the particle number and density develop various asymptotic and intermediate
dynamic regimes, and nontrivial large-time states when the dissipative
mechanism acts at the center of the system.Comment: 16 page
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