Browsing by Author "ASIM NISAR SHEIKH"

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    Computational study on RU based heusler alloys for electrical and optical responses
    (UMT, Lahore, 2024) ASIM NISAR SHEIKH
    The Opto-Electronic properties of the materials play a vital role in the device fabrication technology. The prime aim of this study is to calculate and compare the common features and dissimilarities in electrical and optical properties of Ruthenium (Ru) stoichiometric based full Heusler alloys (FHAs) for different substitutions. The current study elaborates the calculations of mentioned properties for cubic full Heusler alloys Ru2FeSi1-xSnx, Ru2FeSi1-xGex, Ru2FeSn1-xGex (x = 0, 0.25, 0.75, 1). An overview of optoelectronics, spintronics and half-metallic (HM) materials is described, further the introduction of Heusler alloys (HAs), and their different types with ordered and disordered structures along with their application are discussed. The discussion on understanding the electrical and optical properties of these alloys and their practical implementation is crucial for this study. For the last thirty years Ru-based FHAs have got special consideration owing to their specific unique properties like; high Curie temperature and exclusive attractive tendency for their magnetic response. To design Magnetic Shape Memory and mechanical devices like actuators and micromechanical sensors it is necessary to study and calculate various physical properties of the proposed materials. This has motivated us to study the Ru-based FHAs for their electrical and optical responses by using first principle calculations based on density functional theory (DFT). The calculations are used to investigate the behavior of the materials at the atomic scale and to predict material behavior, without relying on experimental data or empirical parameters having a wide range of applications in fields like material science, chemistry, and physics, including the design of new materials, the understanding of chemical reactions, and the study of physical properties. The key purpose of this study is to investigate the opto-electronic properties of Ru based FHAs for many important technological applications. DFT is implemented into Wien2k package performed by using full potential linearized augmented plane wave (FP+LAPW) method. The Generalized Gradient Approximation amended by Perdew Burke–Ernzerhof (GGA-PBE) and modifed Becke–Johnson potential (mBJ-GGA PBE) is used in Kohn-Sham (K-S) equations as an exchange correlation (XC) functional for the calculation of band gaps and other electrical properties of the alloys. Abstract xix The Materials Simulation techniques and computational modeling through DFT method is used to investigate these properties and to eliminate the complication in growth and characteristic approach. DFT calculations are generally less computationally intensive than other electronic structure methods as these consider the electron density (ED) rather than individual electron wave functions, making them more accessible for large-scale simulations.
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    Yield calculation of positron emitters for high specific activity
    (UMT, Lahore, 2015) ASIM NISAR SHEIKH
    The development of longer lived positron emitter radionuclides,(termed as non-standard positron emitters) are required to study the metabolic processes, labelling of organic compounds leading to analogue tracers (e.g. with halogens) and quantification of targeted therapy. The decay characteristics of those non-standard positron emitters (half-lives, prompt emission of associated gamma rays, positron energy and positron decay fraction) determine the qualitative and quantitative accuracy (i.e. blurring, spatial resolution, sensitivity, radiation dose, etc.) of the image, which ultimately defines their possible utilization in PET. The radioisotopes can be used in clinical trials after standard bench marking. Yield calculation is an integral part of this business. In this work, we will select some positron emitters which may be potentially important in nuclear medicine. The reaction cross section data will lead to calculate the yields. The specific activity will be estimated keeping in view the impurity level in each isotope. The recommended reaction routes will be suggested for the production of selected isotopes for medical applications.