1,720,979 research outputs found
Local fivefold symmetry in liquid and undercooled Ni probed by x-ray absorption spectroscopy and computer simulations
No full textPresence and significance of fivefold configurations in liquid metals are investigated by combining x-ray absorption spectroscopy and computer simulations (molecular dynamics and reverse Monte Carlo) in liquid and undercooled liquid nickel. We show that icosahedral short-range ordering (ISRO), probed by common-neighbor (CNA) and spherical invariant (Wî6) analysis, involves a limited fraction (14-18% in undercooled nickel for different structural models) of local atomic configurations. The emerging picture for the liquid structure is that of a mixture of nearly icosahedral structures embedded in a disordered network mainly composed of fragments of highly distorted icosahedra (40-45% of the total), structures reminiscent of the crystalline phase, and other configurations. © 2014 American Physical Society
DFT model of hydrogen desorption from MgH2: The role of iron catalyst
No full textHydrogen desorption from hydride matrix is still an open field of research. Extensive, density functional theory based, ab-initio molecular dynamics simulations of MgH2-Mg interface catches the atomic level structural mechanism leading to hydrogen desorption. The numerical model estimates the desorption temperature for an interface with Fe catalyst in excellent agreement with experimental results. Formation energies and the analysis of the structural data reveal the role played by the catalysts to lower the desorption temperature. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved
A brief summary of the progress on the EFDA tungsten materials program
No full textThe long-term objective of the European Fusion Development Agreement (EFDA) fusion materials programme is to develop structural and armor materials in combination with the necessary production and fabrication technologies for reactor concepts beyond the International Thermonuclear Experimental Reactor. The programmatic roadmap is structured into four engineering research lines which comprise fabrication process development, structural material development, armor material optimization, and irradiation performance testing, which are complemented by a fundamental research programme on "Materials Science and Modeling." This paper presents the current research status of the EFDA experimental and testing investigations, and gives a detailed overview of the latest results on materials research, fabrication, joining, high heat flux testing, plasticity studies, modeling, and validation experiments. © 2013 Elsevier B.V. All rights reserved
Recent progress in research on tungsten materials for nuclear fusion applications in Europe
No full textThe current magnetic confinement nuclear fusion power reactor concepts going beyond ITER are based on assumptions about the availability of materials with extreme mechanical, heat, and neutron load capacity. In Europe, the development of such structural and armour materials together with the necessary production, machining, and fabrication technologies is pursued within the EFDA long-term fusion materials programme. This paper reviews the progress of work within the programme in the area of tungsten and tungsten alloys. Results, conclusions, and future projections are summarized for each of the programme's main subtopics, which are: (1) fabrication, (2) structural W materials, (3) W armour materials, and (4) materials science and modelling. It gives a detailed overview of the latest results on materials research, fabrication processes, joining options, high heat flux testing, plasticity studies, modelling, and validation experiments. © 2012 Elsevier B.V. All rights reserved
High performance computing on CRESCO infrastructure: research activities and results 2020
Full text linkThis book is a collection of 51 papers, written by the main users of the ENEA CRESCO computing infrastructure. It describes applications related to high performance computing, an important technology for science and engineering. The topics cover many different fields as: materials science, climate, environment, nuclear technology, plasma physics, complex systems, HPC technology and many other advanced research topics which can be afforded only by using a specialized high performance computing. In particular, cause to the pandemic situation, in 2020 part of the computational resources were devoted to research activities finalized at the fight against COVID-19. These researchers employed about 15 % of the overall computing time and yielded 8 works. The CRESCO system is one of the major super-computing infrastructures in Italy; it is used by more than 150 scientists, for research and projects of ENEA, but is also made available to the wider scientific community, with many users belonging to important national and international academic and industrial groups. CRESCO is part of ENEAGRID, the computing infrastructure of ENEA, which is a distributed system covering six ENEA Centers: Portici, Frascati, Casaccia, Brindisi, Bologna and Trisaia. The Portici Center hosts the main computing facilities, where only CRESCO6 cluster has a computing power over than 1,4 PFlop
Scambio termico in transitorio in apparati elettronici in cabinets. Modello numerico e verifica sperimentale
No full textWorkshop sul Controllo Termico dei Dispositivi Elettronici - Associazione Scambio Termico in Elettronica, Politecnico di Milano, Ottobre 199
Porting e benchmark in ambiente multipiattaforma ENEAGRID di codici di calcolo per applicazioni scientifiche, con particolare riguardo per quelli del settore chimica e fisica dei materiali (Parte I)
Full text linkIn questo report descriviamo le principali tematiche affrontate nell’installazione in ambiente multipiattaforma ENEAGRID, di codici di calcolo per applicazioni nel settore della Scienza dei Materiali. Attualmente, l’architettura principalmente utilizzata è Linux x86_64, tuttavia, la descrizione di questo tipo di approccio multipiattaforma, mantiene una sua importanza perché illustra le potenzialità dell’architettura ENEAGRID che permettono flessibilità verso possibili evoluzioni future delle tecnologie per il calcolo scientifico. Inizialmente, verrà presentata l’installazione delle librerie matematiche BLAS e LAPACK. In seguito, presenteremo le fasi per la compilazione e installazione del programma di dinamica molecolare CPMD.
Tale codice verrà utilizzato per lo studio di una interfaccia magnesio-idruro di magnesio, nel contesto dello stoccaggio di idrogeno mediante composti solidi. Infine, verrà testata l’efficienza della parallelizzazione del codice CPMD.In this report, we describe the main issues addressed in the installation of computer codes for applications in the field of Materials Science in ENEAGRID. Currently, the main architecture used is Linux x86_64, however, the description of this type of multiplatform approach, remains important because it illustrates the potentialities of the ENEAGRID architecture that allow flexibility in future evolutions of scientific computing technologies. Initially, the installation steps of the BLAS and LAPACK mathematical libraries are presented. Later, the details for compiling and installing the molecular dynamics program CPMD are given. This code is
used for the study of an interface between magnesium hydride and magnesium, in the context of the hydrogen storage in solid compounds. Finally, the parallelization efficiency of code CPMD is tested
Structural and electronic characterization of Pb adsorption on clean and Cr or Ni doped Fe(1 0 0) surface: An ab-initio study
Full text linkUsing ab-initio calculations, the interaction of lead adatom on both the clean and doped iron (100) surfaces has been investigated. The adsorption energies show that the hollow site provides a more stable configuration with respect to the top and bridge sites, and, in this position, the lead adatom is more energetically favourable than the iron adatom. On the other hand, lead adsorbed in the hollow site of the iron (100) surface doped with chromium, provides more stable system than the nickel doped surfaces with an iron atom adsorbed in the same position. Detailed investigations of inter-layer distances, bonding mechanisms in terms of the projected density of states, magnetic behaviours, and charge density differences are also presented. Our results give insights in the role of the doping the interaction between lead adatom and iron surface, and then, this study may be exploited in the analysis of the corrosion process due to liquid lead
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