V3Ge bileşiğinin fiziksel özelliklerinin ve süperiletkenlik mekanizmasının teorik olarak incelenmesi

Year 2024, , 834 - 850, 15.09.2024

Süleyman Berkutay Dursun , Sadık Bağcı

https://doi.org/10.17714/gumusfenbil.1439901

Abstract

Bu çalışmada Yoğunluk Fonksiyonel Teorisini ele alan Quantum Espresso paket programı kullanılarak A15 tipi V3Ge bileşiğinin yapısal, elektronik, elastik ve fonon özellikleri araştırılmış ve süperiletkenlik mekanizması teorik olarak incelenmiştir. Örgü sabiti hesaplamalarını müteakip hacim modülü ve hacim modülünün basınca göre birinci türevi farklı örgü sabitlerine karşılık gelen enerji değerleri ve Murnaghan durum denklemleri yardımıyla elde edilmiştir. Genelleştirilmiş Gradyan Yaklaşımı ve Yapay Potansiyel Metodu kullanılarak elektronik özelliklere ilişkin hesaplamalar yapılmış ve neticesinde V3Ge bileşiğinin elektronik bant yapısı grafikleri spin-orbit etkileşimi hesaba katılarak ve spin-orbit etkileşimi hariç tutularak ayrı ayrı hazırlanmıştır. Bunun yanı sıra V3Ge kristali için hesaplanan elektron durum yoğunluğu grafiklerinden, V3Ge kristalinin süperiletkenlik mekanizmasının araştırılmasında önemli bir yer tutan Fermi enerjisi civarındaki durum yoğunluğu N(EF), tam-rölativistik ultrasoft yapay potansiyeller kullanılarak hesaplanmıştır. Süperiletken materyallerin elastik özelliklerinin araştırılması, süperiletkenlik özelliklerinin teorik olarak anlaşılabilmesi için de oldukça önemlidir. Bu nedenle bu çalışmada V3Ge bileşiğinin elastik özellikleri ayrıntılı olarak ele alınmıştır. Elastik sabitlerin değerleri, Gerilme-Gerinim (Stress-Strain) metodu kullanılarak elde edilmiştir. V3Ge’nin süperiletkenlik özelliklerinin incelenebilmesi için fonon özelliklerinin de incelenmesi gerekir. Fonon hesaplamaları neticesinde ortalama fonon frekansı ve elektron-fonon etkileşim parametresi elde edilmiştir. Bu parametre değerleri ve Migdal-Eliashberg yaklaşımı kullanılarak V3Ge bileşiğinin süperiletkenliğe geçiş kritik sıcaklığı ortaya konmuştur.

Keywords

A15 tipi, Elektronik özellikler, Fonon özellikler, Süperiletkenlik, Yapısal özellikler, Yoğunluk Fonksiyonel Teorisi

Theoretical Investigation of the physical properties and superconductivity mechanism of V3Ge compound

Abstract

In this study, the superconductivity mechanism was theoretically examined by investigating the structural, electronic, elastic and phonon properties of the A15 type V3Ge compound using the Quantum Espresso package program, which deals with Density Functional Theory. Following the lattice constant calculations the bulk modulus and the first derivative of the bulk modulus with respect to pressure were with the help of energy values corresponding and different lattice constants and Murnaghan equations of state. Calculations regarding the electronic proerties were made using the Generalized Gradient Approach and Pseudopotential Method and as a result, the electronic band structure graphs of the V3Ge compound were prepared separately by including the spin-orbit interaction in the calculation and excluding the spin-orbit interaction. In addition, from the electronic density of states graph calculated for the V3Ge crystal, the density of states at the Fermi level, N(EF), which has an important place in the investigation of the superconductivity mechanism of the V3Ge crystal was calculated using full-relativistic ultrasoft pseudopotentials. Investigation of the elastic properties of superconducting materials is also very important for the theoretical understanding of superconductivity properties. Therefore, in this study, the elastic properties of the V3Ge compound are discussed in detail. Elastic constant values have been obtained by using the Stress-Strain method. In order to investigate the superconductivity properties of V3Ge, phonon properties should be analysed. As a result of the phonon calculations, the average phonon frequency and electron-phonon interaction parameter were obtained. These parameter values were used to reveal the critical temperature of the V3Ge compound for transition to superconductivity using the Migdal-Eliashberg approach.

Keywords

A15 type, Electronic properties, Phonon properties, Superconductivity, Structural properties, Density Functional Theory

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