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Article Citation - WoS: 5Citation - Scopus: 4Pressure and Spin Effect on the Stability, Electronic and Mechanic Properties of Three Equiatomic Quaternary Heusler (fevhfz, Z = Al, Si, and Ge) Compounds(Elsevier, 2021) Surucu, G.; Gencer, A.; Surucu, O.; Usanmaz, D.; Candan, A.In this paper, three equiatomic quaternary Heusler compounds -FeVHfZ (Z = Al, Si, and Ge) - are investigated for their structural, magnetic, electronic, mechanic, and lattice dynamic properties under pressure effect. These compounds are optimized for under three structural types and three magnetic phases: beta is the most stable structure with ferromagnetic phase. The electronic properties reveal that FeVHfAl is a half-metal, and that FeVHfSi and FeVHfGe are spin gapless semiconductors. In addition to electronic band structure, possible hybridization and partial density of states are presented. Furthermore, the mechanical properties are studied, and the three-dimensional direction-dependent mechanical properties are visualized under varying pressure effects. Our results reveal the half-metal and spin gapless semiconductor nature of the ferromagnetic FeVHfZ com-pounds, making them promising materials for spintronics applications.Article Citation - WoS: 12Citation - Scopus: 12First Principles Study of Bi12geo20< Electronic, Optical and Thermodynamic Characterizations(Elsevier, 2021) Isik, M.; Işık, Mehmet; Surucu, G.; Gencer, A.; Gasanly, N. M.; Işık, Mehmet; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringBismuth germanium oxide (Bi12GeO20) is one of the attractive members of sillenite compounds having fascinating photorefractive characteristics. The electronic, optical and thermodynamic properties of Bi12GeO20 were investigated using density functional theory (DFT) calculations. The experimental and calculated X-ray diffraction patterns were obtained as well-consistent with each other. The lattice constant of the cubic crystalline structure of Bi12GeO20 compound was calculated as 10.304 angstrom. The electronic band structure and partial density of states plots were reported and contribution of constituent atoms (Bi12GeO20) to the valence and conduction bands was presented. The band gap energy of the Bi12GeO20 was calculated as 3.20 eV. This wide direct band gap energy provides Bi12GeO20 significant potential in ultraviolet applications. The spectra of real and imaginary components of dielectric function, refractive index, extinction coefficient and absorption coefficient were drawn in the 0-10 eV energy range. Temperature-dependent heat capacity plot indicated the Dulong-Petit limit as 825 J/mol.K. The results of the present study would present worthwhile information to device application areas of Bi12GeO20 compound.
