LiTiAl Yarı-Heusler Alaşımının Yapısal, Elastik, Elektronik ve Titreşimsel Özelliklerinin İlk İlkeler Yöntemleri Kullanılarak İncelenmesi

Heusler alaşımları özellikle spintronik ve termoelektrik uygulamalarda önemli ölçüde dikkat çekmektedir. Son zamanlarda sıklıkla tartışılan enerji krizi ve çevresel kirlilikten dolayı yeni ve daha iyi termoelektrik malzemelerdeki araştırmalar hızla artmaktadır. Termoelektrik malzemeler bu problemlerin çözümü için potansiyel yollardan biri olarak görülmektedir. Yarı-Heusler malzemelerde büyük sıcaklık kararlılıklarından dolayı termoelektrik malzemeler olarak düşünülmektedir. Tipik olarak yarı-Heusler alaşımlar uzay gruplu (No.216) yüzey merkezli kübik yapıda kristallenir. Bu çalışmada ilkel hücresinde 8 elektrona sahip Li tabanlı LiTiAl bileşiğinin yapısal, elastik, elektronik ve titreşimsel özellikleri ilk ilkesel yöntemler kullanan VASP paket programı kullanılarak incelenmiştir. Hesaplamalarda 700 eV kesilim enerjisi ve 15x15x15 k-noktası kullanılmıştır. Örgü sabiti 6.191Å olarak hesaplanmıştır. Elde edilen yapısal parametreler mevcut literatür sonuçları ile uyumludur. Elektronik özellikler olarak band yapısı, toplam ve kısmi durum yoğunluğu grafikleri çizilmiştir. Bu hesaplardan bu bileşiğin band aralığı 9.55 meV olarak bulunmuştur. Elastik sabitleri zor-zorlanma oranından hesaplanmıştır. Hesaplanan elastik sabitleri bu bileşiğin mekaniksel olarak kararlı olduğunu göstermiştir. Fonon frekansları hesaplanmıştır ve yapı kararlı olarak bulunmuştur.

Anahtar Kelimeler:

LiTiAl, Yarı-Heusler, Titreşimsel özellikler, DFT, GGA-PBE

Investigation on Structural, Elastic, Electronic and Vibrational Properties of LiTiAl Half-Heusler Compound Using First Principles Methods

Heusler alloys are particularly noticeable in spintronics and thermoelectric applications. The researches on new and better thermoelectric materials are increasing rapidly due to the energy crisis and environmental pollution which are frequently discussed in recent times. Thermoelectric materials are seen as potential ways to solve these problems. Half-Heusler materials are considered thermoelectric materials due to their large temperature stability. Typically, half-Heusler crystallizes in a face-centered cubic structure with alloys space group (No.216). In this study, the structural, elastic, electronic and vibrational properties of the Li-based LiTiAl compound with 8 electrons in the primitive cell were investigated using the VASP package program using the first principles methods. The 700 eV cutoff energy and 15x15x15 k-points were used in calculations. The lattice constant has been calculated as 6.191Å. The obtained structural parameteres are convenient with the results of literature. Band structures, total and partial density states graphs are drawn as electronic properties. From these calculations, the band gap of this compound was found to be 9.55 meV. Elastic constants were calculated from stress-strain rate. The calculated elastic constants show that this compound is mechanically stable. Phonon frequencies are calculated and the structure is found dynamically stable.

Keywords:

LiTiAl, Half-Heusler, Vibrational properties, DFT, GGA-PBE.,

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