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Fullerene Superconductors
Published in David A. Cardwell, David C. Larbalestier, I. Braginski Aleksander, Handbook of Superconductivity, 2023
Yoshihiro Iwasa, Kosmas Prassides
In this chapter, we will attempt to provide a background for understanding the electronic properties of fullerene intercalation compounds, and to deduce the chemical, structural and physical criteria for the occurrence of superconductivity. In order to do so, the next section will begin with the characterization of fullerene intercalation compounds in terms of their molecular valence (band filling) and will explain how alkali-doped and alkaline-earth–doped superconductors differ from each other in the conditions that produce superconductivity. The third section will discuss the electronic properties of trivalent fullerides, where superconductivity is destroyed by a Mott–Hubbard transition, possibly induced by the expansion of the interfullerene spacing or reduction in symmetry of the crystal structure. In the fourth section, a comparison between alkali- and alkaline-earth–doped systems focusing on the A4C60 type structure is presented. These arguments demonstrate that, in fullerene intercalation compounds, the competition or cooperation of the electron–electron interaction and the electron–phonon interactions play important roles in determining the electronic ground state including superconductivity. Superconductivity is strongly dependent on the band filling as well as on the symmetry of the crystal structure. The last two sections address the recent developments in the field. These encompass the discovery of a superconductivity dome (the first unambiguous evidence of unconventional non-BCS phenomenology); the revelation that the metallic and superconducting states emerge from an antiferromagnetic insulating precursor (signature of the importance of electronic correlations in determining the pairing interaction); and the visualization of the evolution of the parent Mott insulator into a normal Fermi liquid state via a “bad” Jahn–Teller (JT) metal state in which itinerant metallic electrons co-exist in a dynamic, microscopically heterogeneous fashion with localized electrons, which produce JT on-molecule distortions.
Convenient connection technology data model supporting optimized information exchange between CAx-systems
Published in Computer-Aided Design and Applications, 2018
Alexander Kreis, Mario Hirz, Severin Stadler, Markus Salchner, Patrick Rossbacher
Another discussion issue is which file formats can be used for the data exchange process. For exchanging assemblies/parts (no CT parts), a converted STEP or JT file instead of the native CAD data (i.e. CATIA or NX files) is a common way. Both, converted data and native data, are possible to be implemented into most CAE or CAM pre-processors, like ANSA. An important issue that is an advantage for a converted file – like JT – is the file size. Fig. 5 shows that a complete JT-file is approximately one-tenth and a JT-ULP-file (ULP … Ultra-Lightweight Precise) nearly a hundredth of the size of a non-converted NX file. This smaller file size allows a faster input process. In most cases the neutral file format is geometrically accurate enough for the pre-processing steps. Disadvantage of using a JT-file include the converting process from native data to a JT-file. This converting process can cause some problems and is time-consuming [6].
Challenges when creating a cohesive digital twin ship: a data modelling perspective
Published in Ship Technology Research, 2021
Ícaro Aragão Fonseca, Henrique Murilo Gaspar
In the absence of an established ship model standard in the industry, alternatives for modelling product data are few and niche, examples of which include some formats and libraries for CAD and 3D visualization (e.g. IGES, STEP, and JT). Gaspar (2019) describes the current scenario of ship software integration as consisting of two trends – suites of PDM and PLM systems by major software providers that offer tools for a ship’s lifecycle and specialised tools that allow more flexible connections with such suites. The following sections discuss some extant approaches proposed to model ship data, which are mentioned as a reference point for subsequent examination of how a multidisciplinary digital twin can be modelled and developed.