Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
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Article Pressure-Induced Polyamorphic Transition and Stepwise Ordering to Superhard B-Doped Diamond-like BC3(Elsevier Science SA, 2026-04) Durandurdu, MuratWe employ constant-pressure ab initio molecular dynamics simulations to investigate the pressure-induced phase transformations of amorphous BC3, which initially possesses a graphite-like layered structure. Our simulations reveal a first-order polyamorphic transition marked by a significant volume collapse and an increase in atomic coordination from a predominantly sp(2) network to a dense, tetrahedrally coordinated sp(3) network. Subsequent thermal annealing of the high-pressure phase uncovers a multi-step ordering process involving a metastable paracrystalline intermediate that bridges the high-density amorphous state and a thermally induced boron-doped diamond-like phase. All high-pressure phases are quenchable to ambient conditions, importantly retaining their semiconducting electronic structures across these transformations. Mechanical characterization demonstrates substantial stiffening, with bulk moduli ranging similar to 252 to 323 GPa. These findings illuminate novel and accessible routes to superhard semiconducting BC3 phases stabilized by pressure and temperature, with the boron-doped diamond-like phase identified as a metastable superhard semiconductor that is thermodynamically favored over the amorphous precursor but kinetically accessible only via the stepwise pathway described. This offers promising directions for advanced material design under extreme conditions.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.