1,721,071 research outputs found
Inclusion of infrared dielectric screening in the GW method from polaron energies to charge mobilities
Full text linkWe introduce in the many-body GW scheme the modulation of the screened Coulomb interaction W arising from the macroscopic dielectric response in the infrared. We derive expressions for the polaron binding energies, the renormalization of the effective masses and for the electron and hole relaxation times. Electron and hole mobilities are then obtained from the incorporation of appropriate scattering rules. Zinc-blende GaN and orthorhombic MAPbI(3) are used as test beds finding fair agreement with results from rigorous electron-phonon coupling approaches. Although limited to polar phonons, our method has a negligible computational cost
Bethe-Salpeter equation approach with electron-phonon coupling for exciton binding energies
No full textWe introduce a simple scheme in order to account for the coupling with longitudinal phonons within the first-principles Bethe-Salpeter approach based on many-body perturbation theory. This allows one to evaluate the reduction of exciton binding energies observed in polar semiconductors. The electron-phonon coupling is modeled from the macroscopic dielectric response in the infrared which, in turn, is calculated through density functional perturbation theory. In this way, the additional computational cost determined by our method is negligible. We first illustrate our approach in the case of bulk ZnS. Then, we discuss the limit of the Bethe-Salpeter equation in the case of strongly delocalized excitons and we show how the excitonic series of bulk Cu2O is well reproduced
A Fully Linear Response G(0)W(0) Method That Scales Linearly up to Tens of Thousands of Cores
Full text link[Image: see text] We present a G(0)W(0) approach that is based on the evaluation of the linear response of the actions of the G(0) and W(0) operators. In this way we avoid sums over empty one-particle orbitals and do not have to explicitly develop the screened Coulomb interaction W(0) on a dedicated basis. For a given orbital, the self-energy is found by summing terms relative to a set of points in the real-space simulation cell. This permits us to easily control the ratio of the accuracy to the computational cost. A trivial parallelization strategy allows strong linear scaling up to tens of thousands of computing cores
Partial resection of the kidney for renal cancer
No full textThe widespread use of abdominal imaging led to an increased early detection of small renal masses in asymptomatic patients. Minimally invasive surgery as laparoscopy and robot-assisted surgery are widely used techniques for kidney surgery particularly for small renal masses. In this chapter robot-assisted partial nephrectomy (RAPN) is meticulously described and perioperative, functional and oncologic outcomes are widely discussed
Training and education in robotic surgery: Recommendations of ERUS (EAU robotic urology section)
No full textThe present chapter aims to give an overview of the importance of training in robotic surgery. It includes the past experiences in robotic urological surgery, the introduction of virtual reality simulation and more advanced training modalities as the wet lab and modular training. This text will highlight the major problems encountered when developing a robotic program and the possible solutions to maximize the available resources of each center. It summarizes today’s available academic programs and assessment tools for knowledge and surgical skills acquisition. Finally, it emphasizes on the necessity of a standardized program with defined educational objectives and the urge for an international standardized certification process. This chapter also explains the attractive robotic curriculum from the European Association of Urology Robotic Urology Section (ERUS). It is proposed as a well-structured program to be universally adopted in training centers providing a stepwise scheme able to endue experienced and unexperienced surgeons the opportunity to perform robotic surgery at the end of the course
Optimal representation of the polarization propagator for large-scale GW calculations
No full textQuasiparticle calculations based on the GW approximation are enhanced by introducing an optimal basis set for the polarization propagator, based on a Wannier representation of the one-electron wave functions, thus allowing the treatment of substantially larger systems. Our method is validated by calculating the vertical ionization energies of the benzene molecule and the band structure of bulk silicon. Its potentials are then demonstrated by addressing the quasiparticle spectrum of a model structure of vitreous silica, as well as of the tetraphenylporphyrin molecule
Importance of semicore states in GW calculations for simulating accurately the photoemission spectra of metal phthalocyanine molecules
No full textThe quasi-particle energy levels of the Zn-Phthalocyanine (ZnPc) molecule calculated with the GW approximation are shown to depend sensitively on the explicit description of the metal-center semicore states. We find that the calculated GW energy levels are in good agreement with the measured experimental photoemission spectra only when explicitly including the Zn 3s and 3p semicore states in the valence. The main origin of this effect is traced back to the exchange term in the self-energy GW approximation. Based on this finding, we propose a simplified approach for correcting GW calculations of metal phthalocyanine molecules that avoids the time-consuming explicit treatment of the metal semicore states. Our method allows for speeding up the calculations without compromising the accuracy of the computed spectra
GW quasiparticle spectra from occupied states only
No full textWe introduce a method that allows for the calculation of quasiparticle spectra in the GW approximation, yet avoiding any explicit reference to empty one-electron states. This is achieved by expressing the irreducible polarizability operator and the self-energy operator through a set of linear response equations, which are solved using a Lanczos-chain algorithm. We first validate our approach by calculating the vertical ionization energies of the benzene molecule and then show its potential by addressing the spectrum of a large molecule such as free-base tetraphenylporphyrin
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
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