Physics Memoir - Journal of Theoretical & Applied Physics

Delineation of Horizontal Locations and Estimation of Depth to Magnetic Source Geometries of Dubumbali, North-East Nigeria

2021-04-23T16:54:44+00:00

Identification of magnetic source geometries of causative bodies is an important procedure when prospecting for hydrocarbon signatures from aeromagnetic data. In order to achieve this purpose, three methods namely Wavelet transform technique (WTT), Fourier transform technique (FTT) and Euler deconvolution technique (EDT) were applied to the reduced to equator (RTE) magnetic data. The WTT applied to the data is based on Morlet wavelet to determine the horizontal locations of magnetic source distribution in the potential field anomalies. These anomalies are always superimposed upon one another in frequency and space domain making it difficult to identify magnetic sources which are of adjacent sources. In view of this, each of the profile data was convoluted with the continuous wavelet transform and the square of coefficients from the convoluted profiles were plotted against the pseudo-wave number. Also, a scaled normalization factor was introduced on the coefficients so that the resolution of various adjacent magnetic sources can be revealed. Depth to magnetic sources was obtained using the FTT, while EDT is used to identify and estimate depth to various magnetic source geometrics with prescribed values of structural indices ranging from 1.0 to 3.0. From this analysis, we have been able to use both WTT and EDT to identify various magnetic source geometries which are attributed to volcanic intrusive rocks found to be predominant in the area while the results of depth estimate using both FTT and EDT ranges from 250 m to 1800 m. The study concluded that the methods are not only useful in the identification and estimation of source geometries due to magnetic anomalies alone, their combinations have served as a tool for identifying hydrocarbon signatures within the study area.

Ab initio Studies of the Structural, Electronic and Mechanical Properties of Zn_1-xCr_xTe

2022-04-12T13:54:38+00:00

The structural, electronic, and mechanical properties of Zn_1-xCr_xTe alloys (for x = 0, 0.25, and 1) have been investigated using ab initio plane-wave ultrasoft pseudopotential calculations based on the density functional theory (DFT). The calculations have been carried out within the local density approximation (LDA), generalized gradient approximation (GGA), and Meta-GGA (TB09) exchange-correlation functionals as implemented in the Quantum Espresso suite of codes and Elk Full-Potential Linearized Augmented Plane-wave (FP-LAPW) codes. As it is well known that LDA and GGA underestimate experimental band gaps, we made attempts to improve on the calculated band gaps using Gaussian-Perdew-Burke-Ernzerhof (Gau-PBE), hybrid functionals, and TB09. We found that the use of TB09 gives the best estimation for the electronic band gap within $\approx1\%$ error. The calculated lattice constants are all in good agreement with the experimental results. The p-type doped ZnTe with chromium (Cr) atom was also investigated (50$\%$ Cr impurity added). The Zinc-blende (ZB) CrTe shows a magnetic property, and electronic structure calculations suggest that it may have applications in spintronics. A $1 \times 2 \times 2$ super-cell (25$\%$ Cr impurity added) was created to further study the effects of impurities on the electronic and mechanical properties of ZB ZnTe. The results show changes in the lattice parameters, electronic properties, and mechanical properties. The three materials satisfy the mechanical stability conditions, which suggests that they are all mechanically stable. They are also anisotropic. Moreover, ZnTe and $\mathrm{Zn}_{3}\mathrm{Cr}\mathrm{Te}_{4}$ are ductile while CrTe is brittle.

The Effect of Active Layer Thickness on the Performance of Tin Halide Perovskite (CH_3NH_3SnI_3)

2021-07-07T12:14:11+00:00

The effect of active layer thickness on the electrical properties of Tin Halide Perovskite (CH_3NH_3SnI_3) was studied using the General-purpose Photovoltaic Device Model (GPVDM) software which is an efficient tool in simulating optoelectronic devices. The simulation was based on some semi-empirical results, and the parameters were inputed to definite materials of each active layer of the solar cell while parameters such as operational temperature and suggestive resistance were based on default entry of the GPVDM simulation software. Absorber thickness was varied from 100nm to 1000nm while other parameters were kept constant. Optimum efficiency of 13.9% was obtained by absorber layer with 600nm thickness, with fill factor and open circuit voltage values decreasing as the absorber thickness increases. Results also showed that the efficiency of this device can be improved by adjusting the active layer thickness.