185 research outputs found

    Editorial

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    Editoria

    Editorial

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    Editoria

    Erfaringer fra 10 års frontforskning med førsteårsuniversitetsstuderende

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    Kommentar til Birgitte Lund Nielsen, Rikke Frøhlich Hougaard, Mikkel Krægpøth: Forskningslignende laboratorieaktiviteter for 1. års studerende på universitetet – muligheder og udfordringer, MONA 2020‑

    Structure of amorphous Ge8Sb2Te11: GeTe-Sb2Te3 alloys and optical storage

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    The amorphous structure of Ge8Sb2Te11, an alloy used in the Blu-ray Disc, the de facto successor to digital versatile disk (DVD) optical storage, has been characterized by large-scale (630 atoms, 0.4 ns) density-functional/molecular-dynamics simulations using the new PBEsol approximation for the exchange-correlation energy functional. The geometry and electronic structure agree well with available x-ray diffraction data and photoelectron measurements. The total coordination numbers are Ge: 4.0, Sb: 3.7, and Te: 2.9, and the Ge-Ge partial coordination number is 0.7. Most atoms (particularly Sb) prefer octahedral coordination but 42% of Ge atoms are "tetrahedral." Structural details, including ring statistics, local coordination, and cavities (12% of total volume), are strikingly similar to those of Ge2Sb2Te5, which is used in DVD-random access memory. The presence of less than 10% Sb atoms leads to significant changes from GeTe
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