Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Tuning Properties of Amorphous Boron Via Hydrogenation: An Ab Initio Study(Elsevier, 2026-01) Durandurdu, MuratAb initio simulations are employed to investigate the structural, mechanical, and electronic properties of hydrogenated amorphous boron (a-B:H) across a range of hydrogen concentrations (approximate to 6-21 at.%). The results indicate that pentagonal-like boron clusters constitute the primary structural motifs. The bonding environment consists of both B-H terminal bonds and B-H-B bridging bonds, with the fraction of bridging bonds ranging from 10 % to 16 %. Increasing the hydrogen content leads to a reduction in density and bulk modulus, accompanied by a systematic widening of the electronic band gap. These results demonstrate that hydrogen incorporation profoundly modifies the atomic structure, softens the network, and enhances the semiconducting character of a-B:H, highlighting the tunability of properties in boron-based amorphous materials.Article Pressure-Induced Quenchable Superhard Tetrahedral Amorphous Phase of BC4N(Wiley, 2025-03-13) Durandurdu, MuratThe high-pressure behavior of an amorphous boron carbon nitride (BC4N) composition is investigated using constant-pressure ab initio molecular dynamics simulations. A first-order phase transformation into a tetrahedral amorphous phase with a high fraction of sp3 bonding is observed. This tetrahedral phase is quenchable and exhibits ultra-high incompressibility and a high Vickers hardness (46 GPa), placing it firmly in the category of superhard materials, comparable to tetrahedral amorphous carbon. Tetrahedral amorphous BC4N demonstrates semiconducting behavior with a narrow bandgap of 0.4 eV, making it suitable for applications requiring both mechanical robustness and moderate electronic conductivity. Thermodynamic analyses confirm the likelihood of a first-order sp2-to-sp3 transition, suggesting that such a transformation could occur around 29 GPa under experimental conditions.Article Citation - WoS: 1Amorphous to Amorphous Phase Transformation in Boron-Rich Amorphous Silicon Borides: An Ab Initio Study(Taylor & Francis Ltd, 2024-05-24) Karacaoglan, Aysegul Ozlem Cetin; Durandurdu, MuratThis study employs a constant-pressure ab initio approach to investigate the high-pressure behavior of five distinct boron-rich amorphous silicon borides. A unique amorphous-to-amorphous phase transition is exposed, providing insights into the structural resilience of these materials under extreme conditions. Our results reveal a gradual increase in the coordination number of both B and Si atoms under pressure, with subsequent densification upon pressure release. Yet the recovered amorphous phases closely resemble the uncompressed states, highlighting the reversibility of these phase changes. Significant structural modifications around Si atoms are observed, emphasizing their pivotal role in the observed phase transitions. Additionally, pressure-induced metallization is witnessed in these materials, indicating their distinctive electronic behavior under high pressure. This work significantly contributes to a deeper understanding of the high-pressure behavior of boron-rich amorphous silicon borides and opens avenues for exploring their potential applications in fields requiring exceptional structural stability and unique pressure-dependent properties.Article Amorphous Silicon Nanoparticles and Silicon Nanoglasses From Ab Initio Simulations(Springer, 2024-04-26) Bolat, Suleyman; Durandurdu, MuratThe 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.Article Citation - WoS: 2Citation - Scopus: 2A First Principles Study of Amorphous and Crystalline Silicon Tetraboride(Elsevier Science SA, 2021-01) Karacaoglu, Ayseguel Ozlem; Durandurdu, MuratUsing first principles simulations, we generate an amorphous silicon tetraboride (SiB4) network from the melt and compare it structurally, mechanically and electrically with the crystal. Surprisingly the amorphous form is found to be energetically more favourable than the crystal. In both phases, the average coordination number of B atoms is comparable but that of Si atom is considerably different. Si atoms have a trend to structure in higher coordinated motifs in the amorphous configuration compared to the crystal. A close examination reveals that pentagonal pyramid-like arrangements are the leading units for B atoms in the noncrystalline state as in the crystal and some of which involve B12 and B11Si type molecules. Both phases exhibit a semiconducting character but have a significantly different band gap value (0.16 eV vs 0.88 eV). The Bulk modulus and Vicker's hardness are predicted to be similar to 151 GPa and 16.1-17.4 GPa for the amorphous network and to be similar to 161 GPa and 18.1-20.2 GPa for the crystal, correspondingly.