Scopus İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395

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  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Structural and Electronic Transformations of GeSe2 Glass Under High Pressures Studied by X-Ray Absorption Spectroscopy
    (Natl Acad Sciences, 2024-03-27) Mijit, Emin; Durandurdu, Murat; Rodrigues, Joao Elias F. S.; Trapananti, Angela; Rezvani, S. Javad; Rosa, Angelika Dorothea; Di Cicco, Andrea; Javad Rezvani, S.
    Pressure-induced transformations in an archetypal chalcogenide glass (GeSe2) have been investigated up to 157 GPa by X-ray absorption spectroscopy (XAS) and molecular dynamics (MD) simulations. Ge and Se K-edge XAS data allowed simultaneous tracking of the correlated local structural and electronic changes at both Ge and Se sites. Thanks to the simultaneous analysis of extended X-ray absorption fine structure (EXAFS) signals of both edges, reliable quantitative information about the evolution of the first neighbor Ge-Se distribution could be obtained. It also allowed to account for contributions of the Ge-Ge and Se-Se bond distributions (chemical disorder). The low-density to high-density amorphous-amorphous transformation was found to occur within 10 to 30 GPa pressure range, but the conversion from tetrahedral to octahedral coordination of the Ge sites is completed above similar to 80 GPa. No convincing evidence of another high-density amorphous state with coordination number larger than six was found within the investigated pressure range. The number of short Ge-Ge and Se-Se "wrong" bonds was found to increase upon pressurization. Experimental XAS results are confirmed by MD simulations, indicating the increase of chemical disorder under high pressure.
  • Article
    Amorphous Silicon Nanoparticles and Silicon Nanoglasses From Ab Initio Simulations
    (Springer, 2024-04-26) Bolat, Suleyman; Durandurdu, Murat
    The structural and electrical characteristics of spherical amorphous silicon nanoparticles (Si-NPs) with radii ranging from 9 to 15 & Aring;, and silicon nanoglasses (Si-NGs) formed by compressing identical-sized Si-NPs, are being investigated for the first-time using ab initio simulations. Analysis reveals predominantly fourfold coordination within Si-NPs, accompanied by noticeable coordination defects. The prevalence of fourfold coordination increases with increasing Si-NP size. Si-NGs, while exhibiting similar dominant fourfold coordination, possess a small fraction of coordination defects (5-8%) primarily concentrated at the interfaces of compressed Si-NPs. Si-NGs are found to have a more open structure compared to amorphous Si. This structural variation, along with observed distortions within Si-NGs, is hypothesized to contribute to a significant narrowing of their band gaps relative to amorphous Si.