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Paolo Giannozzi

Bio: Paolo Giannozzi is an academic researcher from University of Udine. The author has contributed to research in topics: Density functional theory & Ab initio. The author has an hindex of 38, co-authored 122 publications receiving 44408 citations. Previous affiliations of Paolo Giannozzi include Nest Labs & École Polytechnique Fédérale de Lausanne.


Papers
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Journal ArticleDOI
TL;DR: La relaxation du reseau est essentielle pour obtenir la passivation des impuretes dans GaAs.
Abstract: Les sites d'equilibre, les frequences vibrationnelles, et les proprietes electroniques de H interstitiel sont etudies par approximation de densite locale. Deux sites differents dans GaAs sont examines: si remplacant un atome de Ga (Donneur Si Ga ) et Si remplacant un atome de As (Si As accepteur). La relaxation du reseau est essentielle pour obtenir la passivation des impuretes

22 citations

Posted Content
TL;DR: In this article, the Eliashberg function and the electron-phonon coupling constant were calculated using Vanderbilt's ultrasoft pseudopotentials, and the results for several properties under pressure, including lattice constant and bulk modulus, were presented.
Abstract: merical accuracy We give a few advices for an efficient calculation of the electron-phonon coupling Some of the technical details, however, can be used in general for calculations of other properties which require an accurate numerical integration with the delta function This paper is organized as follows: In the next Section we remind the physical definitions and give some details of the calculation of electron-phonon interaction coefficients using Vanderbilt’s ultrasoft pseudopotentials 10 In Sec III, we give the technical details (Subsec A) and present results for several properties under pressure: the lattice constant and bulk modulus (Subsec B), the band structure and Fermi surface (Subsec C), the phonon frequencies and linewidths (Subsec D), and the Eliashberg function and electron-phonon coupling constant (Subsec E) In Sec IV, we discuss the origin of the anomalies, and we summarize in Sec V In the Appendix, we give numerical details for the calculation of the Eliashberg function

19 citations

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TL;DR: In this article, the ground state of Cs2 and Cs+2 was calculated in the local spin density approximation of density functional theory, and different approximations for the core electrons in the derivation of ab initio norm-conserving pseudopotentials.
Abstract: We present the results of several calculations of the ground state of Cs2 and Cs+2 performed in the local‐spin‐density approximation of density functional theory, and using different approximations for the core electrons in the derivation of ab initio norm‐conserving pseudopotentials. We investigate the influence of both core polarization and relativistic effects on the molecular bonding, which turns out to be of minor importance for the determination of the equilibrium characteristics. We find that in order to guarantee an accurate description within the one‐electron scheme, one must avoid the usual ‘‘linear’’ approximation of the exchange‐correlation functional in the derivation of the pseudopotentials. This introduces significant errors for Cs and most probably for all one‐electron systems.

19 citations

Journal ArticleDOI
TL;DR: In this paper, photoluminescence and Raman measurements have been carried out as a function of In content (y) in relaxed and strained InyAl1−yAs alloys grown by molecular beam epitaxy on InP.
Abstract: Photoluminescence and Raman measurements have been carried out as a function of In content (y) in relaxed and strained InyAl1−yAs alloys grown by molecular‐beam epitaxy on InP. From the analysis of photoluminescence data near the lattice matched condition a reliable energy‐gap dependence on In content for the strained material has been derived. From this the Bir–Pinkus electronic deformation potentials at the lattice matched condition have been determined. The Raman results for the relaxed material have been interpreted in the framework of the modified random element isodisplacement theory, yielding the localized Al mode in InAs, the gap In mode in AlAs, and quadratic dependences versus y for the different optical‐phonon frequencies (AlAs‐like and InAs‐like). Optical‐phonon deformation potentials have been calculated within ab initio theory for AlAs and successfully used to fit the AlAs‐like phonon frequencies in strained InyAl1−yAs. Some problems have been found in interpreting the InAs‐like strained pho...

19 citations

Journal ArticleDOI
TL;DR: In this article, the structural and electronic properties of the fullides were analyzed using the Car-Parrinello method as well as standard local density approximation band structure calculations, and it was shown that metal clusters do not form but, like the potassium and rubidium fullerides, sodium intercalation gives rise to a conventional ionic compound.
Abstract: We calculate the structural and electronic properties of the ${\mathrm{Na}}_{6}$${\mathrm{C}}_{60}$ fulleride using the Car-Parrinello method as well as standard local density approximation band structure calculations. In contrast to previous claims we find that metal clusters do not form but, like the potassium and rubidium fullerides, sodium intercalation gives rise to a conventional ionic compound. Unlike the case of heavier alkali fullerides, a characteristic new kind of low-lying electron state appears that is not the ${\mathrm{C}}_{60}$ state. Effects of temperature on the electronic nature of the compound are discussed as well as consequences of these findings for higher fullerides.

18 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: QUANTUM ESPRESSO as discussed by the authors is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave).
Abstract: QUANTUM ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave). The acronym ESPRESSO stands for opEn Source Package for Research in Electronic Structure, Simulation, and Optimization. It is freely available to researchers around the world under the terms of the GNU General Public License. QUANTUM ESPRESSO builds upon newly-restructured electronic-structure codes that have been developed and tested by some of the original authors of novel electronic-structure algorithms and applied in the last twenty years by some of the leading materials modeling groups worldwide. Innovation and efficiency are still its main focus, with special attention paid to massively parallel architectures, and a great effort being devoted to user friendliness. QUANTUM ESPRESSO is evolving towards a distribution of independent and interoperable codes in the spirit of an open-source project, where researchers active in the field of electronic-structure calculations are encouraged to participate in the project by contributing their own codes or by implementing their own ideas into existing codes.

19,985 citations

Journal ArticleDOI
TL;DR: The basics of the suject are looked at, a brief review of the theory is given, examining the strengths and weaknesses of its implementation, and some of the ways simulators approach problems are illustrated through a small case study.
Abstract: First-principles simulation, meaning density-functional theory calculations with plane waves and pseudopotentials, has become a prized technique in condensed-matter theory. Here I look at the basics of the suject, give a brief review of the theory, examining the strengths and weaknesses of its implementation, and illustrating some of the ways simulators approach problems through a small case study. I also discuss why and how modern software design methods have been used in writing a completely new modular version of the CASTEP code.

9,350 citations

Journal ArticleDOI
TL;DR: In this paper, the current status of lattice-dynamical calculations in crystals, using density-functional perturbation theory, with emphasis on the plane-wave pseudopotential method, is reviewed.
Abstract: This article reviews the current status of lattice-dynamical calculations in crystals, using density-functional perturbation theory, with emphasis on the plane-wave pseudopotential method. Several specialized topics are treated, including the implementation for metals, the calculation of the response to macroscopic electric fields and their relevance to long-wavelength vibrations in polar materials, the response to strain deformations, and higher-order responses. The success of this methodology is demonstrated with a number of applications existing in the literature.

6,917 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate phonon properties with fundamental equations and show examples how the phonon calculations are applied in materials science, and demonstrate the importance of first principles phonon calculation in dynamical behaviors and thermal properties.

6,508 citations