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A Study on the Physical Properties of the Newly Calculated Phases of Cu-Al-Be Alloys by iab initio/i Calculations      
Yazarlar
Doç. Dr. Cengiz SOYKAN
Kırşehir Ahi Evran Üniversitesi, Türkiye
Özet
Total energy calculations based on density functional theory were performed to investigate the physical properties for the austenitic L21 and newly calculated martensitic phases of the Cu2 AlBe shape memory alloy. When the total energy of all the phases versus the volume data are fitted to the Birch–Murnaghan equation of state, it is seen that the stable martensitic NM, 3M, 5M, and 7M phases of the alloy can exist. The lowest energetic phase was determined as tetragonal non-modulated NM structure. When we compare the energy of the newly calculated martensitic phases to the thermal fluctuation energy barriers (criteria as (3kBT)/2 meV/atom is taken), we are confident that the energy difference between 5M, 7M, and 9R phases and the NM phase is large enough to overcome the thermal energy barrier. Moreover, it has been observed that the calculated elastic constants of austenitic L21 and martensitic NM, 3M, 5M, 7M, and 9R phases provide all the mechanical stability conditions determined according to crystal structure symmetries. We consider that the phases that exceed the thermal energy barriers and satisfy the mechanical stability conditions can exist at a stable energy level. When the partial electronic density of states (pDOS) of the austenitic and martensitic phases are analyzed, it is seen that the most contribution to the electronic density of states comes from Cu t2g and Cu eg states. In addition, it is seen that the contributions to the electronic density of state from not only s, p, t2g and eg states of Al and Be atoms but also s and p states of Cu atom have been observed extremely small quantity in the all austenitic and martensitic phases. On the other hand, the t2g, and eg states of Cu atoms dominate in the electronic nature of the Cu2AlBe shape memory alloy. Cu2AlBe shape memory alloy is a non-magnetic material since all phases of spin-up and spin-down are all symmetrical.
Anahtar Kelimeler
Makale Türü Özgün Makale
Makale Alt Türü SSCI, AHCI, SCI, SCI-Exp dergilerinde yayımlanan tam makale
Dergi Adı ACTA PHYSICA POLONICA A
Dergi ISSN 0587-4246
Dergi Tarandığı Indeksler SCI-Expanded
Dergi Grubu Q4
Makale Dili İngilizce
Basım Tarihi 09-2019
Cilt No 136
Sayı 3
Sayfalar 411 / 423
Doi Numarası 10.12693/APhysPolA.136.411
Makale Linki http://przyrbwn.icm.edu.pl/APP/PDF/136/app136z3p06.pdf