Malzeme Bilimi ve Makine Mühendisliği Ana Bilim Dalı Tez Koleksiyonu

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Browsing Malzeme Bilimi ve Makine Mühendisliği Ana Bilim Dalı Tez Koleksiyonu by Subject "Abinitio molecular dynamics technique"

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    The simulations of amorphous boron materials
    (Abdullah Gül Üniversitesi, Fen Bilimleri Enstitüsü, 2023) YILDIZ, Tevhide Ayça; AGÜ, Fen Bilimleri Enstitüsü, Malzeme Bilimi ve Makine Mühendisliği Ana Bilim Dalı
    Boron-based materials and their technological applications have great interests in many scientific and technological areas from materials science to medicine. This doctorate thesis was prepared for the purpose of investigating the atomic structure, electrical and mechanical properties of different boron based amorphous materials by using an ab-initio molecular dynamics technique. The results obtained via a computational method were presented in three main chapters. In the Chapter 3, the influence of hydrogenation on the atomic structure and the electronic properties of amorphous boron nitride (ɑ-BN) was examined. The structural evaluation of ɑ-BN and the hydrogenated (ɑ-BN:H) models revealed that their short-range order was mainly similar to each other. Hydrogenation suppressed the formation of twofold coordinated chain-like structures and tetragonal-like rings and leaded to more sp2 and even sp3 bonding. Furthermore, hydrogenation was found to have an insignificant impact on the electronic structure of ɑ-BN. Secondly, in the Chapter 4, an amorphous boron carbide (a-B4C) model was generated. The pentagonal pyramid-like motifs were found to be the main building units of B atoms in a-B4C and some of which yielded the development of B12 icosahedra. On the other hand, the fourfold-coordinated units were the leading configurations for C atoms. a-B4C was a semiconducting material and categorized as a hard material. In the Chapter 5, amorphous boron carbides (BxC1-x, 0.50x0.95) were systematically created. With increasing B/C ratio, more closed packed materials having pentagonal pyramid motifs form. All models were semiconducting materials. Some amorphous compositions were proposed to be hard materials. Keywords: Amorphous, Hydrogenation, Boron Nitride, Boron Carbide, Ab-initio molecular dynamics technique