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Article Citation - WoS: 45Citation - Scopus: 43Investigation of Structural, Electronic, Magnetic and Lattice Dynamical Properties for Xcobi (x: Ti, Zr, Hf) Half-Heusler Compounds(Elsevier, 2020) Surucu, Gokhan; Isik, Mehmet; Candan, Abdullah; Wang, Xiaotian; Gullu, Hasan HuseyinStructural, electronic, magnetic, mechanical and lattice dynamical properties of XCoBi (X: Ti, Zr, Hf) Half-Heusler compounds have been investigated according to density functional theory and generalized gradient approximation. Among alpha, beta and gamma structural phases, gamma-phase structure has been found as the most stability characteristics depending on the calculated formation enthalpies, energy-volume dependencies and Cauchy pressures. Energy-volume plots of possible magnetic orders of gamma-phase XCoBi compounds have been analyzed and the most stable order has been found as paramagnetic nature. The theoretical studies on gamma-phase structures resulted in band gap energies of 0.96, 0.99 and 0.98 eV for TiCoBi, ZrCoBi and HfCoBi semiconducting compounds, respectively. Born-Huang criteria applied on elastic constants of interest compounds has indicated that gamma-phase is also mechanically stable for all studied compounds. In addition, various mechanical, lattice dynamical and thermodynamical parameters of XCoBi compounds have been calculated in the present study.Article Citation - WoS: 8Citation - Scopus: 9First-principles studies of Tin+1SiNn (n=1, 2, 3) MAX phase(Taylor & Francis Ltd, 2020) Surucu, Gokhan; Gullu, Hasan Huseyin; Candan, Abdullah; Yildiz, Bugra; Erkisi, AytacIn this study, the structural, electronic, mechanical, lattice dynamical and thermodynamic characteristics of ( 1, 2 and 3) phase compounds were investigated using the first principle calculations. These ternary nitride compounds were found to be stable and synthesisable, and the results on the stability nature of them were also evaluated for the possible and phases. -was found to be the most stable one among these new class of layered phases for which limited works are available in the literature. The band structures, that are essential for the electronic properties, were determined along with the partial density of states (PDOS) indicating the metallic behaviour of these compounds. The polycrystalline elastic moduli were calculated based on the single-crystal elastic constants and the mechanical stabilities were verified. Some basic physical parameters, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Debye temperature, and sound velocities, were also predicted. Furthermore, the anisotropic elastic properties were visualised in three dimensions (3D) for Young's modulus, linear compressibility, shear modulus and Poisson's ratio as well as with the calculation of the anisotropic factors. - phase showed the most isotropic characteristics with minimum deviations. These theoretical values were also used to identify the stiffness and ionic characteristics. The phonon dispersion curves and corresponding PDOS indicated that compounds were dynamically stable. Moreover, thermodynamic properties obtained from phonon dispersion curves were investigated in detail.Article Citation - WoS: 23Citation - Scopus: 24First Principles Study on the Structural, Electronic, Mechanical and Lattice Dynamical Properties of Xrhsb (x = Ti and Zr) Paramagnet Half-Heusler Antimonides(Iop Publishing Ltd, 2019) Surucu, Gokhan; Candan, Abdullah; Erkisi, Aytac; Gencer, Aysenur; Gullu, Hasan HuseyinThe half-Heusler TiRhSb and ZrRhSb alloys in the formation of face-centered cubic MgAgAs-type structure, which conforms to the F (4) over bar 3m space group with 216 as the space number, have been investigated using Generalized Gradient Approximation (GGA) implemented in Density Functional Theory (DFT). The calculated formation enthalpies and the plotted energy-volume curves of different types of structural phases (alpha, beta, and gamma) in these alloys indicate that the gamma-phase structure is the best energetically suitable structure. In addition, TiRhSb and ZrRhSb alloys have been found as paramagnetic (PM) with the investigation of antiferromagnetic (AFM), ferromagnetic (FM), and paramagnetic (PM) orders in the most stable gamma-phase structure. Therefore, their electronic, mechanical, and dynamical properties have been examined in the gamma structural phase and paramagnetic order. These alloys have semiconducting nature due to the observed same band gaps in both the majority and minority spin channels of the calculated spin-polarised electronic band structure. These calculated band gaps are 0.75 eV for gamma-TiRhSb and 1.18 eV for gamma-ZrRhSb. The predicted elastic constants indicate that the alloys in this study are mechanically stable and show nearly isotropic behavior in the gamma structural phase. Also, the minimum and the diffuson thermal conductivites have been determined for these alloys. Finally, the calculated phonon dispersion spectras for the gamma-TiRhSb and gamma-ZrRhSb half-Heusler antimonide alloys show the dynamic stability of these systems.Article Citation - WoS: 154Citation - Scopus: 153First-Principle Investigation for the Hydrogen Storage Properties of Naxh3 (x= Mn, Fe, Co) Perovskite Type Hydrides(Pergamon-elsevier Science Ltd, 2019) Surucu, Gokhan; Candan, Abdullah; Gencer, Aysenur; Isik, MehmetIn the present study, NaXH3 (X = Mn, Fe, Co) perovskite type hydrides have been investigated by performing first-principles calculation. The results of the structural optimizations show that all these compounds have negative formation energy implying the thermodynamic stability and synthesisability. The mechanical stability of these compounds has been studied with the elastic constants. Moreover, the polycrystalline properties like bulk modulus, Poisson's ratio, etc. have been obtained using calculated elastic constants of interest compounds. The electronic properties have been studied and band structures have been drawn with the corresponding partial density of states. These plots indicated that NaXH3 hydrides show metallic characteristics. The charge transfer characteristics in these compounds have been studied with the Bader partial charge analysis. The phonon dispersion curves and corresponding density of states indicated that NaXH3 compounds are dynamically stable compounds. The investigation on hydrogen storage characteristics of NaXH3 compounds resulted in hydrogen storage capacities of 3.74, 3.70 and 3.57 wt% for X = Mn, Fe and Co, respectively. The present study is the first investigation of NaXH3 perovskite type hydrides as known up to date and may provide remarkable contribution to the future researches in hydrogen storage applications. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
