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    Öğe
    Computational investigations of mechanic, electronic and lattice dynamic properties of yttrium based compounds
    (World Scientific Publ Co Pte Ltd, 2018) Yildiz, Gokcen Dikici; Yildiz, Yasin Gokturk; Selgin, A. L.; Iyigor, Ahmet; Arikan, Nihat
    Electronic, mechanic and lattice dynamic properties of yttrium-based compounds, X3Y, where X = Pd, Pt and Rh were investigated using the density functional theory. The electronic band calculations demonstrated that X3Y compounds are metallic at the cubic crystal structures. The calculated elastic constants using the energy-strain method indicate that the three materials are mechanically stable. The calculated bulk modulus and Young's modulus values suggest that the Pt3Y is stiffer than that of the other two. The type of bonding and ductility in the X3Y compounds were also evaluated based on their B/G ratios, Cauchy pressures (C-12-C-44) and band structure calculations. These compounds were found to be ductile in nature. The density functional perturbation theory was used to derive full phonon frequencies and total and projected phonon density of states. The computed full phonon spectra for X3Y compounds show that these compounds in the L1(2) phase are dynamically stable. Debye temperature and specific heat of these compounds were also calculated and evaluated using quasi harmonic approximation.
  • Küçük Resim
    Öğe
    Electronic, Elastic, Vibrational and Thermodynamic Properties of HfIrX (X = As, Sb and Bi) Compounds: Insights from DFT-Based Computer Simulation
    (SPRINGER, 2020) Arikan, Nihat; Dikici Yildiz, Gokcen; Yildiz, Yasin Gokturk; Iyigor, Ahmet
    Ab-initio calculations were performed to reveal and thoroughly understand the structural, electronic, elastic, thermodynamic and vibrational properties of HfIrX (X = As, Sb and Bi) compounds in the C1(b) phase. Basic physical characteristics, such as bulk modulus, pressure derivative of bulk modulus, anisotropy factor, shear modulus, Poisson's ratio, Cauchy pressure, elastic constants and Young's modulus were obtained and some of them were compared with those in the literature. Electronic band structure, the density of states and phonon dispersion curves were obtained and compared with current theoretical calculations. It was concluded according to current band structure calculations that the HfIrAs and HfIrBi compounds showed semimetal characteristics, while the HfIrSb compound behaves as a semiconductor. It was determined based on phonon calculations that all three compounds were dynamically stable. Various thermodynamic properties, such as heat capacity, thermal expansion coefficient values and Gruneisen parameter were calculated under constant volume and constant pressure by using Gibbs2 code within the Quasi-harmonic approach, and these results are discussed.