Browsing by Subject "First principles calculation"

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    Structural, electronic, and mechanical properties of A3Mn2O7 (A = Sr, Ca): ab initio calculation
    (Taylor & Francis, 2019) Şimsek, Ş.; Koç, H.; Mamedov, Amirullah M.; Özbay, Ekmel
    In the present study, the structural, electronic, optical, and mechanical properties of the Ruddlesden-Popper type oxide compounds are investigated by means of density functional theory. In our calculation, spin polarized electron band structures and density of the state were identified by adding to the spin contribution of the Mn-atom. For A3Mn2O7 compounds, the real and imaginary parts of the dielectric function and other optical properties, such as energy loss function, effective number of valence electrons, and effective optical dielectric constant, were calculated accordingly. In addition, the bulk modules, shear modules, Young's modulus and Poisson ratios, anisotropy factors, sound velocities, and Debye temperatures for these compounds were calculated too.
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    A theoretical study on silicon and III-V compound nanotubes
    (TÜBİTAK, 2005) Durgun, Engin; Çıracı, Salim
    In this paper we present a theoretical study on single-wall silicon and III-V compound nanotubes. First principles plane wave calculations within density functional theory are used to predict energetics and electronic structures of armchair and zigzag nanotubes. The stability of tubular structures is further investigated at finite temperature by ab initio molecular dynamics calculations. Our results indicate that (n,0) zigzag and (n,n) armchair single-wall Si nanotubes are stable for n ≥ 6. Mechanically, the Si nanotubes are radially soft, however they are strong against axial deformations. Electronic analysis showed that zigzag nanotubes are metallic for n ≤ 11, but they show semiconducting behavior for larger radii. On the other hand, all armchair nanotubes are metallic. (8,0) single wall nanotube has been chosen as prototypes for AlP, GaN, and GaAs compounds and we found that they are semiconducting and stable at room temperature. © TÜBİTAK.