Theoretical and Applied PhysicsThis collection contains selected research work by Theoretical and Applied Physics Students at the master's level, from 2009-2022.http://repository.aust.edu.ng/xmlui/handle/123456789/4612024-03-29T06:10:33Z2024-03-29T06:10:33ZAB Initio Study of Surface Energy, Surface Stress and Coupling Coefficient of Au (111)Shehu, Mustaphahttp://repository.aust.edu.ng/xmlui/handle/123456789/51372023-12-18T22:01:50Z2023-12-10T00:00:00ZAB Initio Study of Surface Energy, Surface Stress and Coupling Coefficient of Au (111)
Shehu, Mustapha
This study investigates ab initio exploration of the Au (111) surface within the generalized gradient approximation, with a primary focus on assessing the convergence properties of this noble metal. An in-depth analysis of the material's response to various computational parameters, including cutoff energy, K-point sampling, and lattice parameter, was conducted to ensure the reliability and consistency of the findings. The theoretical determination of the lattice constant, yielding a value of 4.059 Å, not only aligns quantitatively with experimental measurements but also agrees with calculated values. A noteworthy aspect of this investigation involves reporting on the work
function's response to strain, shedding light on how this essential property evolves under external
influences. Additionally, the study evaluates the variation of energy per unit cell with varying slab
thickness, providing insights into the material's behavior across different structural configurations. The results reveal that Au (111) exhibits a surface energy of 0.5561 𝑒𝑉Å−1, surface stress of 0.18177 𝑒𝑉Å−2and a coupling coefficient of 1.145 eV. These results provides significant implications for understanding the mechanisms associated with electrochemical coupling at an atomic scale, offering crucial insights into the material's behavior across diverse atomic and electronic structures. Thus this work contribute to the understanding of Au (111) surface properties, laying a foundation for advancements in understanding electrochemical phenomena and fostering the development of tailored applications in materials science and nanotechnology.
Main Thesis
2023-12-10T00:00:00ZModeling of the Origin and Interactions of Multisoliton Solutions of the (2+4)KdV EquationNingang, Julius Mbuitohhttp://repository.aust.edu.ng/xmlui/handle/123456789/50662022-08-26T21:00:42Z2019-06-05T00:00:00ZModeling of the Origin and Interactions of Multisoliton Solutions of the (2+4)KdV Equation
Ningang, Julius Mbuitoh
Most of the relevant research work has addressed the properties of internal solitons in a greatly simplified environment, usually in the framework of different versions of the two layer fluid. The simplest equation of this class is the well-known Korteweg-de Vries (kdV)
equation that describes the motion of weakly nonlinear internal waves in the long-wave limit. However, in many areas of the world’s ocean, the vertical stratification has a clearly pronounced three-layer structure, with well-defined seasonal thermocline at a depth of
about 100m or higher. Hence , the need for a redefinition of the famous KdV equation to tackle such scenarios and clearly accounts for nonlinearity in such environments. In this work, we first derived an analytical solution for the (2+4) KdV-like equation which mimics
such situations and numerically solved it using the pseudospectral methods due to its robustness. After numerical simulations, we observed that the multisoliton solution interactions, particularly the three soliton solution interaction showed similar properties with the two soliton solution interaction.
2019 Theoretical and Applied Physics Masters Theses
2019-06-05T00:00:00ZFemtosecond laser pulses interacting with atomsMoses, Eshovo Ojohttp://repository.aust.edu.ng/xmlui/handle/123456789/50652022-08-26T21:00:39Z2019-09-16T00:00:00ZFemtosecond laser pulses interacting with atoms
Moses, Eshovo Ojo
We theoretically investigated a phenomena arising from the interaction of femtosecond pulsed lasers with an Hydrogen atom. The phenomena of interest to us, is the High or der Harmonic Generation (HHG) of soft and hard-Xray using linearly polarized two-color
femtosecond laser pulses. This HHG process is a commonly employed technique to pro duce ultrashort intense light spanning through the ultraviolet to the x-ray region of the Electromagnetic Spectrum (EM). The development of HHG which has opened fascinat ing research at sub- atomistic scale is however been delimited by its lower higher-order harmonics, and the possibility of obtaining a single burst of attosecond (which is of high important, since significant amount of the laser energy are carried by single pulses) are been compromised. We began addressing this challenge, by solving the 1D non-relativistic Schr¨odinger equation for an H atom using the dipole approximation, whose solution was obtained by the split operator method. We separately computed the HHG spectrum due to a Titanium-Sapphire (fundamental field) and an arbitrary pulsed laser (secondary field) in the far-visible region. When the fundamental Ti:Sapphire laser field with the param eters; 800 nm, 2×1014W/cm2 and 10 cycles, were allowed to irradiate the H atom, we observed a train of 1330 as pulses extending from the 8th - 36th harmonic order, and whose energy measured 12 eV -55.8 eV . By considering the interaction of a similar Ti:Sapphire laser, with a different intensity of 4×1014W/cm2, we observed a train of 677 as pulses extending from the 25th - 75th harmonic order and whose energy measured 39 eV - 116 eV . When the secondary laser source in the far visible region with the parameters; 400 nm, 5×1014W/cm2 and 20 cycles irradiated the H atom, a train of 1209 as pulses extending from the 28th - 50th harmonic order, and whose energy corresponds to 87 eV - 155 eV was generated. Furthermore, by synthesizing the fundamental and secondary laser, and upon irradiation with the H atom, an HHG spectrum with a broad plateau whose energy spans through the ultraviolet region up to the hard X-ray region was observed. The broadness of the plateau implies the generation of short pulses, which also represents a clear indica tion of the possibility of obtaining a single attoseconds pulse. Though by considering a time delay in the synthesized laser there weren’t obvious change of our results, we finally obtained a continuum of abrupt end at the 685th order corresponding to a single pulse of 1.044 keV of energy with a short time duration of 169 as.
2019 Theoretical and Applied Physics Masters Theses
2019-09-16T00:00:00ZStructural and electronic properties of a two-dimensional hybrid system of graphene and hexagonal boron nitride: A first-principles studyMahadi, Rabiatuhttp://repository.aust.edu.ng/xmlui/handle/123456789/50642022-08-26T21:00:33Z2019-06-02T00:00:00ZStructural and electronic properties of a two-dimensional hybrid system of graphene and hexagonal boron nitride: A first-principles study
Mahadi, Rabiatu
Despite the excellent properties of graphene, graphene based electronic devices are yet to be realized, one of the reason for such is the absence of band gap in graphene. Due to its large band gap, hexagonal boron nitride (h-BN) is not suitable for electronic application. Here, we present a new method of tailoring the electronic properties of both graphene and h-BN by making a 2-d hybrid containing both materials. In this study, we investigate the structural and electronic properties of graphene/h-BN lateral hybrid using DFT at different proportions. Our result shows that, as the proportion of h-BN in the hybrid is increased, band gap opens in the range of 0.64 - 1.1 eV. This suggest that our hybrid is semiconducting and can be used for different electronic applications. Even though the structural
parameters of the hybrid changes with increasing concentration of h-BN, the formation energy of the hybrid increases as the proportion of h-BN in the hybrid is increased, thus this proposed hybrid is very stable.
2019 Theoretical and Applied Physics Masters Theses
2019-06-02T00:00:00Z