Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 3Citation - Scopus: 3Phase Transition of ZrN Under Pressure(Taylor & Francis Ltd, 2019-01-14) Durandurdu, MuratA first principles constant pressure approach is carried out to probe the high-pressure behaviour of the rocksalt (RS) structured zirconium nitride (ZrN). The existence of first order reconstructive phase transition from the RS crystal to a CsCl-type crystal is, for the first time, established throughout the simulations. Upon decompression, the CsCl type phase converts back to the original RS structure by following the same transformation mechanism, suggesting a reversible phase transformation in ZrN. The RS-to-CsCl phase change is additionally considered through the thermodynamic theorem and projected to take place at around 225 GPa in experiments. The structural parameters and mechanical properties computed are found to be comparable with some of the previous findings. Additionally, we investigate the response of ZrN to uniaxial compression and tension stresses. The uniaxial stresses initially lead to a tetragonal modification of the simulation box having an I4/mmm symmetry and subsequently structural failure that is expected to occurs at about -10 and 15 GPa in experiments.Article Citation - WoS: 3Citation - Scopus: 4Nanosegregated Amorphous AlBN2 Alloy(Taylor & Francis Ltd, 2016-09-14) Durandurdu, MuratWe use ab initio molecular dynamics simulations to create an amorphous AlBN2 model and find that it consists of nanosegregated two-dimensional hexagonal BN-like and tetrahedral AlN-like domains. These domains are somewhat homogenously distributed in the network. There exist no chemical disorder and Al-B bonding. Amorphous AlBN2 is a semiconductor having a theoretical band gap energy of approximate to 2.24eV, larger than that of amorphous AlN and BN systems. This amorphous nitride might find some applications as an electronic material.Article N-Type Conductivity in Si-Doped Amorphous Aln: An Ab Initio Investigation(Taylor & Francis Ltd, 2016-03-11) Durandurdu, MuratWe report the electronic structure and topology of a heavily Si-doped amorphous aluminium nitride (Al37.5Si12.5N50) using ab initio simulations. The amorphous Al37.5Si12.5N50 system is found to be structurally similar to pure amorphous aluminium nitride. It has an average coordination number of about 3.9 and exhibits a small amount of Si-Si homopolar bonds. The formation of Si-Al bonds is not very favourable. Electronic structure calculations reveal that the Si doping has a negligible effect on the band gap width but causes delocalization of the valence band tail states and a shift of the Fermi level towards the conduction band. Thus, amorphous Al37.5Si12.5N50 alloys show n-type conductivity.Article Citation - WoS: 2Citation - Scopus: 2MgCu Metallic Glass(Taylor & Francis Ltd, 2017-12-10) Durandurdu, MuratWe generate an amorphous MgCu model using the rapid solidification of the melt through a first-principles molecular dynamics approach within a generalised gradient approximation and reveal, for the first time, its structural features and mechanical properties in details. The liquid and glassy MgCu are found to acquire slightly distinct local structures. Yet in both forms of MgCu, most Cu atoms have a tendency to form the ideal and defective icosahedrons while Mg atoms are arranged in complex configurations. The mean coordination number of Cu and Mg at 300 K is 11.31 and 13.73, respectively. The short-range order of MgCu glass is projected to be different than the known crystalline MgCu and Mg2Cu phases. The mechanical properties of MgCu glass and the CsCl-type MgCu crystal are computed and compared. On the basis of the enthalpy analyses, a possible pressure-induced crystallisation of the MgCu glass into a CsCl-type structure is proposed to occur at around 11 GPa.Article Irreversible Changes in Amorphous C3n4 Under Pressure: Loss of Chemical Order and Graphite-Like Character(Taylor & Francis Ltd, 2025-04-03) Durandurdu, MuratThe high-pressure behavior of triazine-based amorphous C3N4, initially exhibiting a chemically ordered, graphite-like structure, was investigated using ab initio molecular dynamics simulations. Our study reveals a pressure-induced transition to a high-density amorphous (HDA) phase characterized by increased coordination number for carbon (3.88) and nitrogen (2.93) atoms. This transition occurs gradually over a broad pressure range, initiated by the breakdown of chemical ordering and the formation of homopolar C-C and N-N bonds, which persist in both the HDA and recovered phases. The recovered phase retains elevated coordination numbers (C: 3.25, N: 2.46) but loses its initial graphite-like topology, evolving into a three-dimensional network structure. Electronic structure analysis reveals semiconducting behavior in the HDA phase and n-type semiconductor characteristics in the recovered phase.Article Citation - WoS: 3Citation - Scopus: 3High-Pressure Phase Transitions of TiN: An Ab Initio Constant Pressure Study(Taylor & Francis Ltd, 2015-07-03) Durandurdu, MuratAn ab initio constant pressure molecular dynamics technique is carried out to explore the behaviour of rock salt-structured titanium nitride (TiN) under pressure. Two successive phase transformations are successfully observed in the dynamical simulations. The first one is an isostructural phase transition accompanied by an anomalous volume compression without any symmetry breaking. The second one is a reconstructive phase transformation into a CsCl-type structure. For the first time, the previously proposed two-phase transformations for TiN are confirmed through the simulations.Article Citation - WoS: 3Citation - Scopus: 3Ferromagnetism in Amorphous MgO(Taylor & Francis Ltd, 2017-05-10) Durandurdu, MuratWe report, for the first time, the atomic structure of amorphous MgO based on ab initio molecular dynamics simulations. We find that its main building blocks are four-fold and five-fold coordinated configurations, similar to those formed in the liquid state. Its average coordination is estimated to beabout 4.36. The amorphous form having a perfect stoichiometry has a band gap energy of 2.4eV. On the other hand, Mg vacancies induce an insulator to metal transition and ferromagnetism in amorphous MgO whilst O vacancies do not cause such a transition, implying that the magnetism in amorphous MgO is related to the non-stoichiometry and Mg vacancies. With the application of pressure, the stoichiometric and non-stoichiometric (Mg vacancies) models undergo a phase transformation into a rocksalt state, suggesting that the electronic structure of the initial configurations has no influence on the resulting high-pressure phase in amorphous MgO.Article Citation - WoS: 10Citation - Scopus: 10Amorphous Zirconia: Ab Initio Molecular Dynamics Simulations(Taylor & Francis Ltd, 2017-02-23) Durandurdu, MuratWe investigate the short-range order of the liquid and amorphous zirconia using an ab initio molecular dynamics technique. Both forms of zirconia are projected to be structurally close to each other. The amorphous network has predominantly seven-fold coordinated Zr atoms (similar to% 65), and three-fold and four-fold coordinated O atoms (similar to 46%), and hence it resembles locally the monoclinic zirconia phase. Within the known limitations of the DFT-GGA calculation, the liquid state is predicted to be semi-metal, whereas the amorphous form is projected to be semiconductor having a band gap energy of similar to 3.5 eV. We find an asymmetry in localisation of the band tail states. On the basis of this finding, we discuss possible distinctions in n-type and p-type doping in amorphous zirconia.Article Citation - WoS: 3Citation - Scopus: 3Amorphous Silicon Hexaboride: A First-Principles Study(Taylor & Francis Ltd, 2018-07-29) Durandurdu, MuratWe report for the first time the atomic structure, electronic structure and mechanical properties of amorphous silicon hexaboride (a-SiB6) based on first-principles molecular dynamics simulation. The a-SiB6 model is generated from the melt and predominantly consists of pentagonal pyramid-like configurations and B-12 icosahedral molecules, similar to what has been observed in most boron-rich materials. The mean coordination number of B and Si atoms are 5.47 and 4.55, respectively. The model shows a semiconducting behaviour with a theoretical bandgap energy of 0.3eV. The conduction tail states are found to be highly localised and hence the n-type doping is suggested to be more difficult than the p-type doping for a-SiB6. The bulk modulus and Vickers hardness of a-SiB6 are estimated to be about 118 and 13-17GPa, respectively.Article Citation - WoS: 5Citation - Scopus: 5Amorphous Silicon Hexaboride at High Pressure(Taylor & Francis Ltd, 2020-03-14) Durandurdu, MuratWe investigate the pressure-induced structural phase transformation of amorphous silicon hexaboride (a-SiB6) using a constant pressure first principles approach. a-SiB6 is found to undergo a gradual phase transformation to a high-density amorphous phase (HDA) in which the average coordination number of both B and Si atoms is about 6. The HDA phase consists of differently coordinated motifs ranging from 4 to 8. B-12 icosahedra are found to persist during compression of a-SiB6 and the structural modifications primarily occur around Si atoms and in the regions linking pentagonal pyramid-like configurations to each other. Upon pressure release, an amorphous structure, similar to the uncompressed one, is recovered, indicating a reversible amorphous-to-amorphous phase change in a-SiB6. When the electronic structure is considered, the HDA phase is perceived to have a wider forbidden band gap than the uncompressed one.