الفهرس 
Chapter I :IntroductionOnly 14 pages are availabe for public view
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Abstract
Firstly, the influence of mechanical bending to tuning the hydrogen storage of Ni-functionalized of zigzag type of boron nitride nanotubes (BNNTs) has been investigated using density functional theory (DFT) with reference to the ultimate targets of the US Department of Energy (DOE). Single Ni atoms prefer to bind strongly at the axial bridge site of BN nanotube, and each Ni atom bound on BNNT may adsorb up to five, H2 molecules, with average adsorption energies per hydrogen molecule of )-1.622--0.527 eV( for the undeformed B40N40-φ = 0º , ) -1.62 - 0-0.308 eV( for the deformed B40N40-φ = 15º, ) -1.589- -0.310 eV( for the deformed B40N40-φ = 30º, and ) -1.368- -0.323 eV( for the deformed B40N40-φ = 45º nanotubes respectively. with the H-H bonds between H2 molecules significantly elongated. The curvature attributed to the bending angle has effect on average adsorption energies per H2 molecule. With no metal clustering, the system gravimetric capacities are expected to be as large as 5.691 wt % for 5H2 Ni B40N40-φ = 0º, 15º, 30º, 45º. While the desorption activation barriers of the complexes nH2 + Ni B40N40-φ = 0º (n = 1-4) are outside the (DOE) domain (-0.2 to -0.6 eV), the complexes nH2 + Ni- B40N40-φ = 0º (n = 5) is inside this domain. For nH2 + Ni- B40N40-φ = 15º, 30º, 45º with (n = 1-2) are outside the (DOE) domain, the complexes nH2 + Ni- B40N40-φ = 15º, 30º, 45º with (n = 3-5) are inside this domain. The hydrogen storage of the irreversible 4H2+ Ni- B40N40-φ = 0º, 2H2+ Ni- B40N40-φ = 15º, 30º, 45º and reversible 5H2+ Ni- B40N40-φ = 0, 3H2+ Ni- B40N40-φ = 15º, 30º, 45º interactions are characterized in terms of density of states, pairwise and non-pairwise additivity, infrared, Raman, electrophilicity and molecular electrostatic potentials. Our calculations expect that 5H2- Ni- B40N40- = 0º, 15º, 30º, 45º complexes are promising hydrogen storage candidates.
Secondly, The effect of axial deformation on tuning the hydrogen storage of nickel functionalized (8, 0) zigzag boron nitride nanotube is investigated by using density functional theory calculations. The assessment has been carried out based on the adsorption of molecular hydrogen with the binding energy lying in the desirable energy window, charge transfer, the density of states, pairwise and nonpairwise additivty, frontier orbital band gaps , isosurface plots, polarizabilities and hyperpolarizabilities, simulated Infrared (IR) and Raman (R). The numerous changes in adsorption energy of H₂ upon relaxation or compression of only (1%) strain points to the sensitivity of H₂ binding to axial deformation effects. The calculated pairwise and non-pairwise additive components show that the role of the BNNT is not restricted to support the metal. Spectral analysis additionally as polarizability and hyperpolarizability calculations characterize the relaxed structure (Z=1.01), that H2 adsorption energy (-0.552 eV) is within the suggested energy vary for hydrogen storage, to be energetically additional desirable than the compressed structure (Z=0.99). The results provide some way to manage and characterize the hydrogenation process of metal functionalized BNNTs by strain loading.