Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Citation - WoS: 6Citation - Scopus: 5Amorphous Boron Carbide From Ab Initio Simulations(Elsevier, 2020-02) Yildiz, Tevhide Ayca; Durandurdu, MuratAn amorphous boron carbide (a-B4C) model is generated by means of ab-initio molecular dynamics calculations within a generalized gradient approximation and its structural, mechanical and electrical features are discussed in details. The mean coordination number of B and C atoms is estimated to be 5.29 and 4.17, respectively. The pentagonal pyramid-like motifs for B atoms, having sixfold coordination, are the main building units in a-B4C and some of which involve with the development of B-12 icosahedra. On the other hand, the fourfold-coordinated units are the leading configurations for C atoms. Surprisingly the formation of C-C bonds is found to be less favorable in the noncrystalline network, compared to the crystal. a-B4C is a semiconducting material having an energy band gap considerably less than that of the crystal. A noticeably decrease in the mechanical properties of B4C is observed by amorphization. Nonetheless a-B4C is categorized as a hard material due to its high Vickers hardness of about 24 GPa.Article Citation - WoS: 3Citation - Scopus: 2Ab Initio Study of Boron-Rich Amorphous Boron Carbides(Wiley, 2023-01-10) Yildiz, Tevhide Ayca; Durandurdu, MuratAmorphous boron carbide compositions having high B contents (BxC1-x, 0.50 <= x <= 0.95) are systematically created by way of ab initio molecular dynamics calculations, and their structural, electrical, and mechanical characteristics are inclusively investigated. The coordination number of both B and C atoms increases progressively with increasing B/C ratio and more close-packed materials having pentagonal pyramid motifs form. An amorphous diamond-like local arrangement is found to be dominant up to 65% B content, and beyond this content, a mixed state of amorphous diamond- and B-like structures is perceived in the models because sp(3) hybridization around C atoms is still leading one for all compositions. The pentagonal pyramid motifs around C atoms are anticipated to appear beyond 65% content. The intericosahedral linear C-B-C chains do not form in any model. All amorphous boron carbides are semiconducting materials. The mechanical properties gradually increase with increasing B concentration, and some amorphous compositions are proposed to be hard materials on the basis of their Vickers hardness estimation.