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 Citation - WoS: 4Citation - Scopus: 4Very Low Density Amorphous Phase of Zircon(Elsevier Science Bv, 2019-06) Bolat, Suleyman; Durandurdu, MuratUsing a reliable ab initio molecular dynamics method, we investigate the rapid solidification of the zircon melt. Accompanied by amorphization, a drastic volume expansion of 27% is perceived. This value is fairly larger than 18% observed in the metamict zircon. Such a large volume swelling leads to a significant decrease in the mean coordination number of Zr atoms, which is about 5.66 and the lowest one reported so far. On the other hand, the volume expansion is found to have almost no impact on the average coordination number of Si atoms i.e., they maintain their tetragonal coordination. As suggested by earlier investigations, the polymerization of SiO4 units is witnessed but our model shows the highest polymerization with respect to the previous simulations. Based on our findings, we propose that our model does not represent the metamict zircon but a very low density amorphous phase of zircon.Article Citation - WoS: 6Citation - Scopus: 6Tetrahedral Amorphous Boron Nitride: A Hard Material(Wiley, 2019-09-25) Durandurdu, MuratWe generate a tetrahedrally coordinated amorphous boron nitride (BN) model by means of first principles molecular dynamics calculations and report its mechanical and electrical properties in detail. The amorphous configuration is almost free from chemical disorder and consists of about 20% coordination defects, similar to tetrahedral (diamond-like) amorphous carbon. Its theoretical band gap energy is about 2.0 eV, less than 4.85 eV estimated for cubic BN. The bulk modulus and Vickers hardness of tetrahedral amorphous BN are computed as 206 GPa and 28-35 GPa, respectively. Based on these findings, we propose that tetrahedral noncrystalline BN can serve as electronic and hard materials as well.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 Pressure-Driven Structural Evolution of Amorphous InN(Elsevier, 2025-02) Durandurdu, MuratThrough constant-pressure ab initio simulations, we have uncovered high-pressure phase transformations in amorphous indium nitride for the first time. Our results reveal a distinct two-step progression under compression. Initially, a polyamorphic transition occurs, where the low-density amorphous (LDA) phase transforms into a high-density amorphous (HDA) phase. This HDA structure remains stable in some pressure range and then crystallization initiates, leading to a rocksalt configuration. Upon decompression, the HDA phase reverts to an amorphous network with a slightly higher density and coordination number than the initial LDA state.Article Citation - WoS: 2Citation - Scopus: 2Possible Boron-Rich Amorphous Silicon Borides From Ab Initio Simulations(Springer, 2023-03-10) Karacaoglan, Aysegul Ozlem Cetin; Durandurdu, MuratContextBy means of ab initio molecular dynamics simulations, possible boron-rich amorphous silicon borides (BnSi1-n, 0.5 <= n <= 0.95) are generated and their microstructure, electrical properties and mechanical characters are scrutinized in details. As expected, the mean coordination number of each species increases progressively and more closed packed structures form with increasing B concentration. In all amorphous models, pentagonal pyramid-like configurations are observed and some of which lead to the development of B-12 and B11Si icosahedrons. It should be noted that the B11Si icosahedron does not form in any crystalline silicon borides. Due to the affinity of B atoms to form cage-like clusters, phase separations (Si:B) are perceived in the most models. All simulated amorphous configurations are a semiconducting material on the basis of GGA+U calculations. The bulk modulus of the computer-generated amorphous compounds is in the range of 90 GPa to 182 GPa. As predictable, the Vickers hardness increases with increasing B content and reaches values of 25-33 GPa at 95% B concentration. Due to their electrical and mechanical properties, these materials might offer some practical applications in semiconductor technologies.MethodThe density functional theory (DFT) based ab initio molecular dynamics (AIMD) simulations were used to generate B-rich amorphous configurations.Article Citation - WoS: 4Citation - Scopus: 4Permanent Densification of Amorphous Zinc Oxide Under Pressure: A First Principles Study(Elsevier Science Bv, 2018-02) Tahaoglu, Duygu; Durandurdu, MuratAb initio simulations within a generalized gradient approximation are carried out to investigate the densification mechanism of amorphous zinc oxide (a-ZnO) under hydrostatic pressure. In contrast to the crystalline ZnO, the densification of a-ZnO is found to proceed gradually and is associated with a structural modification from a low density amorphous state to a high density amorphous state. Accompanied by the phase transformation, the mean coordination number increases from similar to 4.0 to similar to 5.5. The high-density amorphous form of ZnO has a local structure, partially comparable with that of the rocksalt type ZnO crystal and presents a semiconducting behavior. The phase change is irreversible because upon pressure release, an amorphous model largely consisting of fivefold coordination is recovered. The decompressed model can be, therefore, classified as an intermediate phase between the wurtzite-like and the rocksalt-like amorphous configurations.Article Citation - WoS: 10Citation - Scopus: 11Liquid Boron and Amorphous Boron: An Ab Initio Molecular Dynamics Study(Elsevier, 2015-06) Durandurdu, MuratThe atomic structure of liquid and amorphous boron is investigated using an ab initio molecular dynamics technique. Liquid and amorphous states are found to have notably different microstructures and an average coordination number. Ideal and defective pentagonal pyramidal polyhedrons are the primary building unit of liquid boron but B-12 icosahedra do not exist in the liquid state. During the rapid solidification, more ideal pentagonal pyramids develop progressively, resulting into a gradual formation of B-12 icosahedra. On the basis of our findings, the atomic packing of pure amorphous boron is proposed to be somewhat close to that of the alpha-rhombohedral phase in contrast to the previous suggestions. (C) 2015 Elsevier B.V. All rights reserved.Editorial Citation - WoS: 4Citation - Scopus: 5Hydrogenated Amorphous Boron Nitride: A First Principles Study(Elsevier, 2018-12) Uchoyuk, Tevhide Ayca; Durandurdu, MuratThe influence of hydrogenation on the atomic structure and electronic properties of amorphous boron nitride (alpha-BN) is investigated by using an ab-initio molecular dynamics technique. The structural evaluation of alpha-BN and the hydrogenated (alpha-BN:H) models with four different hydrogen concentrations reveals that although their short-range order is mainly similar to each other, hydrogenation yields some noticeable amendments on the local structure of alpha-BN. Hydrogenation suppresses the formation of twofold coordinated chain-like structures and tetragonal-like rings and leads to more sp(2) and even sp(3) hybridizations. It is also observed that the formation of N-H bonding is more favorable than that of the B-H bonding in the alpha-BN:H configurations. Furthermore hydrogenation is found to have an insignificant impact on the electronic structure of alpha-BN.Article Citation - WoS: 17Citation - Scopus: 17Hexagonal Nanosheets in Amorphous BN: A First Principles Study(Elsevier Science Bv, 2015-11) Durandurdu, MuratAmorphous boron nitrite is modeled by means of first principles molecular dynamics simulations and found to be almost chemically ordered in a stark contrast to the previous predictions. Its average coordination number is 2.97. The main building unit of the amorphous network is hexagonal rings as in the most stable boron nitrite phase but chain-like structures and tetragonal-like rings also exist in amorphous network. The model consists of partially hexagonal nanosheets and hence it is not entirely disordered. Amorphous boron nitrite has a band gap energy of about 2.0 eV. (C) 2015 Elsevier B.V. All rights reserved.