ZrMo2 ve HfMo2 bileşiklerinin kararlılıklarının Ab-initio yöntemiyle incelenmesi
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Date
2015
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Aksaray Üniversitesi Fen Bilimleri Enstitüsü
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info:eu-repo/semantics/openAccess
Abstract
Bu tez çalışmasında, ZrMo2 ve HfMo2 bileşiklerin kübik C15 (uzay grubu Fd-3m), hekzagonal C14 (uzay grubu P63/mmc), C36 (uzay grubu P63/mmc) ve ortorombik CeCu2 (uzay grubu Imma) yapılarının yapısal, mekanik, elektronik ve örgü dinamiği özellikleri yoğunluk fonksiyoneli teorisine dayanan temel prensipler yöntemiyle incelendi. Bu bileşikler için düşünülen yapılar arasında kübik C15 kristal yapısının en kararlı yapı olduğu görüldü. Hesaplanan elastik sabitlerden hareketle, tüm yapılar elastik kararlılık kriterlerine göre mekaniksel olarak kararlıdır. Aynı zamanda bulk, shear ve Young modülü, Poisson oranı, Debye sıcaklığı, sertlik ve anizotropi gibi bazı mekaniksel özellikler hesaplandı ve yorumlandı. Düşünülen yapılar için fonon dispersiyon eğrileri ve fonon durum yoğunluğu elde edildi ve detaylı olarak tartışıldı. Bu bileşikler için CeCu2 yapısı haricindeki tüm yapılar dinamiksel olarak kararlılık sergilemektedir. Elde edilen sonuçlar mevcut deneysel ve teorik sonuçlar ile uyum içindedir.
In study of this thesis, the structural, mechanical, electronic, and lattice dynamical properties of ZrMo2 and HfMo2 compounds in cubic C15 (space group Fd-3m), hexagonal C14 (space group P63/mmc), C36 (space group P63/mmc), and orthorhombic CeCu2 (space group Imma) structures have been investigated by using the first principles method based on density functional theory. We have found that these compounds in cubic C15 crystal structure are the most stable among the considered structures. From calculated elastic constants, it is shown that all structures are mechanically stable according to the elastic stability criteria. The related mechanical properties such as bulk, shear and Young moduli, Poisson's ratio, Debye temperature, hardness, and anisotropy have been also calculated and commented. The phonon dispersion curves and phonon density of states are also computed and discussed exhaustively for considered phases. The all compounds exhibit dynamical stability for except CeCu2 structure. The obtained results are in the agreement with the available-experimental-and-theoretical-results.
In study of this thesis, the structural, mechanical, electronic, and lattice dynamical properties of ZrMo2 and HfMo2 compounds in cubic C15 (space group Fd-3m), hexagonal C14 (space group P63/mmc), C36 (space group P63/mmc), and orthorhombic CeCu2 (space group Imma) structures have been investigated by using the first principles method based on density functional theory. We have found that these compounds in cubic C15 crystal structure are the most stable among the considered structures. From calculated elastic constants, it is shown that all structures are mechanically stable according to the elastic stability criteria. The related mechanical properties such as bulk, shear and Young moduli, Poisson's ratio, Debye temperature, hardness, and anisotropy have been also calculated and commented. The phonon dispersion curves and phonon density of states are also computed and discussed exhaustively for considered phases. The all compounds exhibit dynamical stability for except CeCu2 structure. The obtained results are in the agreement with the available-experimental-and-theoretical-results.
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Keywords
ZrMo2, HfMo2, Ab-initio, Laves Fazları, Mekaniksel Özellikler, Laves Phases, Mechanical Properties
