Valerio Olevano
Centre national de la recherche scientifique
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Featured researches published by Valerio Olevano.
Zeitschrift Fur Kristallographie | 2005
Xavier Gonze; Gian-Marco Rignanese; Matthieu Verstraete; Jean-Michel Beuken; Yann Pouillon; Razvan Caracas; F. Jollet; M. Torrent; Gilles Zerah; Masayoshi Mikami; Philippe Ghosez; M. Veithen; Jean-Yves Raty; Valerio Olevano; Fabien Bruneval; Lucia Reining; R. W. Godby; Giovanni Onida; Hamann; Dc. Allan
Abstract A brief introduction to the ABINIT software package is given. Available under a free software license, it allows to compute directly a large set of properties useful for solid state studies, including structural and elastic properties, prediction of phase (meta)stability or instability, specific heat and free energy, spectroscopic and vibrational properties. These are described, and corresponding applications are presented. The emphasis is also laid on its ease of use and extensive documentation, allowing newcomers to quickly step in.
Physical Review B | 2011
Xavier Blase; Claudio Attaccalite; Valerio Olevano
We evaluate the performances of ab initio GW calculations for the ionization energies and highest occupied molecular orbital-lowest unoccupied molecular orbital gaps of 13 gas phase molecules of interest for organic electronic and photovoltaic applications, including the C60 fullerene, pentacene, free-base porphyrins and phtalocyanine, PTCDA, and standard monomers such as thiophene, fluorene, benzothiazole, or thiadiazole. Standard G0W0 calculations, that is, starting from eigenstates obtained with local or semilocal functionals, significantly improve the ionization energy and band gap as compared to density functional theory Kohn-Sham results, but the calculated quasiparticle values remain too small as a result of overscreening. Starting from Hartree-Fock-like eigenvalues provides much better results and is equivalent to performing self-consistency on the eigenvalues, with a resulting accuracy of 2%‐4% as compared to experiment. Our calculations are based on an efficient Gaussian-basis implementation of GW with explicit treatment of the dynamical screening through contour deformation techniques.
Physical Review Letters | 2002
Lucia Reining; Valerio Olevano; Angel Rubio; Giovanni Onida
Starting from the many-body Bethe-Salpeter equation we derive an exchange-correlation kernel f(xc) that reproduces excitonic effects in bulk materials within time-dependent density functional theory. The resulting f(xc) accounts for both self-energy corrections and the electron-hole interaction. It is static, nonlocal, and has a long-range Coulomb tail. Taking the example of bulk silicon, we show that the -alpha/q(2) divergency is crucial and can, in the case of continuum excitons, even be sufficient for reproducing the excitonic effects and yielding excellent agreement between the calculated and the experimental absorption spectrum.
Physical Review Letters | 2008
Paolo E. Trevisanutto; Christine Giorgetti; Lucia Reining; Massimo Ladisa; Valerio Olevano
We present an ab initio numerical many-body GW calculation of the band plot in freestanding graphene. We consider the full ionic and electronic structure introducing e-e interaction and correlation effects via a self-energy containing non-Hermitian and dynamical terms. With respect to the density-functional theory local-density approximation, the Fermi velocity is renormalized with an increase of 17%, in better agreement with the experiment. Close to the Dirac point the linear dispersion is modified by the presence of a kink, as observed by angle-resolved photoemission spectroscopy. We demonstrate that the kink is due to low-energy pi-->pi* single-particle excitations and to the pi plasmon. The GW self-energy does not open the band gap.
Physical Review B | 2011
Carina Faber; Claudio Attaccalite; Valerio Olevano; Erich Runge; Xavier Blase
On the basis of first-principles GW calculations, we study the quasiparticle properties of the guanine, adenine, cytosine, thymine, and uracil DNA and RNA nucleobases. Beyond standard G0W0 calculations, starting from Kohn-Sham eigenstates obtained with (semi)local functionals, a simple self-consistency on the eigenvalues allows us to obtain vertical ionization energies and electron affinities within an average 0.11 and 0.18 eV error, respectively, as compared to state-of-the-art coupled-cluster and multiconfigurational perturbative quantum chemistry approaches. Further, GW calculations predict the correct π-character of the highest occupied state, due to several level crossings between density functional and GW calculations. Our study is based on a recent Gaussian-basis implementation of GW calculations with explicit treatment of dynamical screening through contour deformation techniques.
Physical Review Letters | 2005
Fabien Bruneval; Francesco Sottile; Valerio Olevano; Rodolfo Del Sole; Lucia Reining
We propose an alternative formulation of many-body perturbation theory that uses the density-functional concept. Instead of the usual four-point integral equation for the polarizability, we obtain a two-point one, which leads to excellent optical absorption and energy-loss spectra. The corresponding three-point vertex function and self-energy are then simply calculated via an integration, for any level of approximation. Moreover, we show the direct impact of this formulation on the time-dependent density-functional theory. Numerical results for the band gap of bulk silicon and solid argon illustrate corrections beyond the GW approximation for the self-energy.
Physical Review Letters | 2009
Pierre Darancet; Valerio Olevano; Didier Mayou
Nanoelectronic devices smaller than the electron wavelength can be achieved in graphene with current lithography techniques. Here we show that the electronic quantum transport of graphene subwavelength nanodevices presents deep analogies with subwavelength optics. We introduce the concept of electronic diffraction barrier to represent the effect of constrictions and the rich transport phenomena of a variety of nanodevices. Results are presented for Bethe and Kirchhoff diffraction in graphene slits and Fabry-Perot interference oscillations in nanoribbons. The same concept applies to graphene quantum dots and gives new insight into recent experiments in these systems.
Physical Review B | 2010
Paolo E. Trevisanutto; Markus Holzmann; Michel Côté; Valerio Olevano
We present ab initio many-body calculations of the optical absorption in bulk graphite, graphene and bilayer of graphene. Electron-hole interaction is included solving the Bethe-Salpeter equation on top of a GW quasiparticle electronic structure. For all three systems, we observe strong excitonic effects at high energy, well beyond the continuum of
Physical Review B | 2007
Eleonora Luppi; Federico Iori; Rita Magri; Olivia Pulci; Stefano Ossicini; Elena Degoli; Valerio Olevano
\pi \to \pi^*
Physical Review B | 2007
Pierre Darancet; Andrea Ferretti; Didier Mayou; Valerio Olevano
transitions. In graphite, these affect the onset of