WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/394
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Article Citation - WoS: 23Citation - Scopus: 23Pressure-Induced Amorphization of MOF-5: A First Principles Study(Wiley-VCH Verlag GmbH, 2018) Erkartal, Mustafa; Durandurdu, Murat; Erkartal, Mustafa; Durandurdu, MuratAmorphous metal-organic frameworks (MOFs) and the amorphization of crystalline MOFs under mechanical stimuli are attracting considerable interest in last few years. However, we still have limited knowledge on their atomic arrangement and the physical origin of crystalline-to-amorphous phase transitions under mechanical stimuli. In this study, ab initio simulations within a generalized gradient approximation are carried out to investigate the high-pressure behavior of MOF-5. Similar to the previous experimental findings, a pressure-induced amorphization is observed at 2 GPa through the simulations. The phase transformation is an irreversible first order transition and accompanied by around 68% volume collapse. Remarkably, the transition arises from local distortions and, contrary to previous suggestions, does not involve any bond breaking and formation. Additionally, a drastic band gap closure is perceived for the amorphous state. This study has gone some way towards enhancing our understanding of pressure-induced amorphization in MOFs.Article Citation - WoS: 3Citation - Scopus: 3High Pressure Modifications in Amorphous Boron Suboxide: An Ab Initio Study(Elsevier Sci Ltd, 2020) Durandurdu, Murat; Durandurdu, MuratUsing constant pressure ab initio calculations, we probe the high-pressure modifications in amorphous boron suboxide (B6O) consisting of glassy boron trioxide (B2O3) and boron (B) domains up to a theoretical pressure of 100 GPa. At this pressure, the structure remains amorphous. We find a steady increase in the average coordination of both B and oxygen (O) atoms. O atoms mostly attain threefold coordination as in B2O3 glass at high pressures. On the other hand, the mean coordination number of B-atoms reaches six at high pressures and the structural changes in B-rich regions are perceived to be quite analogous to those of amorphous B. B-12 clusters are found to persevere during the pressurizing process and the high-pressure modifications occur predominantly around O-atoms and the regions that connect the pentagonal pyramid-like motifs to each other. Upon pressure release, some high-pressure configurations persist in the model and another noncrystalline structure being about 10% denser than the original state is recovered, suggesting a permanent densification and a possible irreversible amorphous-to-amorphous phase transformation in B6O. The recovered network shows slightly better mechanical properties than the uncompressed model. During the compression and decompression processes, amorphous B6O remains semiconducting. The delocalization of some band tail states is seen at high pressures.