Computation of the total scattering cross sections for the halogens

Calculated Total Cross-Sections (TCS) of elastic electron-atom scattering for F, Cl, Br, I and At are presented. The computed TCS were calculated using Born, Eikonal and the Optical Theorem approximation methods with the Lenz-Jensen potential, at electron incident energies between 1to1000 eV. Results obtained are in good agreement with experimental TCS data.Keywords: Total Cross-Section, elastic scattering, halogens, optical theorem, Born approximation, Eikonal approximatio

Using asymptotic iteration method (AIM) for solving differential equations: case study of vibrational states of diatomic molecule

This paper discusses the new computational technique referred to as the asymptotic iteration method (AIM), and presents numerical computations of exact energy eigenvalues of the Schrödinger equation assuming the Morse potential for some diatomic molecules. The method is used to compute the numerical energies of bound vibrational levels of the 7Li2, H2, and N2 diatomic molecules in the 1Σu+, 11Σu+ and 3Σu+ electronic states

DFT computations of the lattice constant, stable atomic structure and the ground state energy per atom of fullerenes (C60)

This paper presents the most stable atomic structure and lattice constant of Fullerenes (C60). FHI-aims DFT code was used to predict the stable structure and the computational lattice constant of C60. These were compared with known experimental structures and lattice constants of C60. The results obtained showed that the most stable crystalline structure of C60 is the face-centred cubic (fcc) structure, this is in complete agreement with experiment. However, the computed lattice constant of the stable structure is 13.87 Å. This value differs from the experimental value of 14.17Å by 0.3Å.Keywords: Fullerenes, Density Functional Theory (DFT), Atomic Structure, Lattice Constant, Total Energ

Computations of the band structure and linear optical properties of methylammonium bismuth bromide and methylammonium galluim bromide using FHI-aims Code

Ab initio calculations for the Linear Macroscopic Dielectric analyses of CH3NH3BiBr3 and CH3NH3GaBr3 (having 8.33% dopant replacement percentage each) as possible replacements for the Lead based perovskite CH3NH3PbBr3 were done in this work using Perdew–Burke–Ernzerhof functional of Density Functional Theory as implemented by FHI-aims Code. Optimized lattice constants were calculated for CH3NH3BiBr3 and CH3NH3GaBr3 to be 9.10 Å and 8.27 Å respectively. The Lowest Unoccupied Molecular Orbital (LUMO), Highest Occupied Molecular Orbital (HOMO) and calculated band gap, Band Structure and Density of States (DOS) plots were made to analyse the band structures of these crystals and they were found to be metallic with a band gap of 0.00018636 eV and 0.00022286 eV for CH3NH3BiBr3 and CH3NH3GaBr3 respectively. The imaginary and real parts of the inter-band and intra-band contribution to the linear dielectric tensor within the e imagi Random Phase Approximation (RPA) of the optical properties of these perovskites were calculated and an average dielectric tensor of 3.1209467 and 2.789173 was found for CH3NH3BiBr3 and CH3NH3GaBr3 respectively. From the absorption data and dielectric tensor components calculated, both materials have an average absorption peak at frequency of 16.5373nm at 1.006567 MeV, 16.2040nm at 1.227600 MeV respectively, across all cubic planes

Electronic band structure and optical properties of titanium dioxide

In this work the Fritz-Haber Institute ab initio Molecular Simulation (FHI-aims) code was used to investigate and obtain the band energies and linear dielectric functions of the three naturally occurring phases of TiO2 (Rutile, Anatase and Brookite). The exchange-correlation interactions are treated by the PBE. The results of the band gap were obtained to be 1.76 eV for Rutile, 2.07 eV for Anatase and 2.33 eV for Brookite with Rutile having a direct band gap and indirect band gaps for both Anatase and Brookite. The obtained band gaps are in agreement with other theoretical work, especially on the rutile phase. The linear dielectric function was calculated using Random Phase Approximation (RPA) where the average static dielectric function at ω= 0 was obtained as 5.61 for Rutile TiO2, 4.29 for Anatase TiO2 and 2.23 for Brookite TiO2

First principle investigation of robustness surface states on ternary mixed chalcogenide Bi2Te2s

In this paper, we present a theoretical investigation on the electronic structures of bulk ternary mixed chalcogenide Bi2Te2S and its corresponding Bi2Te2S (111) surface thin films based on the first principle within the density-functional theory. The spin-orbit coupling (SOC) included self-consistency. We have found that the effect of SOC significantly changes the electronic properties of bulk Bi2Te2S. For the Bi2Te2S (111) surface thinfilms, we have adopted the method proposed by Park K. et al (2010). Our result shows the presence of robustness states on the electronic structure of Bi2Te2S (111) thin films with the presence of a Dirac Point (DP) below the Fermi level EF that is completely covered in the bulk bands. This result is in agreement with the Topological Insulator (TI) nature in the binary Bi2Te3

First-principles calculations of Fluorine-doped Titanium dioxide: A prospective material for solar cells application

This study focuses on the anatase TiO2 doped Fluorine to investigate their structural and electronics properties using Density Functional Theory (DFT) within generalized gradient approximation (GGA) as implemented in Quantum ESPRESSO (QE). For the anatase TiO2 phase the calculated electronic band structures of pure TiO2 and TiO2 doped Fluorine nanocrystals are displayed along a high symmetry directions and the energy range of band structure is plotted from 0.0 eV to 3.9 eV , the energy separation between the bottom of the conduction band and the top of valence band occurred at the Γ and  points, indicating that  anatase TiO2 is an indirect band gap material with an approximate value of 2.30 eV energy gap, this value is consistent with previous DFT result. When F is added the band structure did not change much because fluorine element doping is conducive to the generation of Oxygen holes and enhances the mobility of effective electrons which can enhance the conductivity of the adsorbent substrate and improve the solar cell performance of the fluorine-doped TiO2. The band gap value obtained for F doped TiO2 was found to be 2.11 eV. The dopant formation energy of Fluorine is calculated to be -55.6 Ry which is equivalent to -756.5 eV.</jats:p

Elman and cascade neural networks with conjugate gradient Polak-Ribière restarts to predict diesel engine performance and emissions fueled by butanol as sustainable biofuel

This study explores the possibility of utilizing green butanol, a promising type of biofuel, in diesel engines to measure its impact on engine performance and emissions. Experimental data were collected on several parameters, including brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature, all of which are influenced by the biofuel type used, in this case, butanol. The study examined emissions such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and smoke opacity. Such emissions have the potential to improve with the use of different biofuels ratios, such as butanol. Advanced machine learning techniques, Elman and Cascade Neural Networks, were employed to predict the performance and emission characteristics of engines using butanol. The models were trained using a Conjugate Gradient Learning Function with Polak-Ribière Restarts to simulate the effects of butanol as biofuel, on diesel engines. Key findings revealed that when incorporating butanol into diesel fuel blends, potential improvements in BTE and fuel efficiency were observed. Notably, using butanol as a biofuel reduced exhaust gas temperatures and CO emissions, demonstrating the potential of this particular biofuel. Conversely, there were observed increases in HC emissions and smoke opacity, signifying the complexities of using biofuels such as butanol. Cascade neural network proved to be highly accurate in predicting engine performance parameters fueled with butanol as biofuel. Overall, the study offers valuable insights into the use of butanol as a biofuel, its potential benefits, and challenges, underscoring the importance of continuous research in sustainable biofuels such as butanol

Corticotropin Tests For Hypothalamic-Pituitary-Adrenal Insufficiency: A Metaanalysis

Context: The diagnostic value of tests for detecting hypothalamic-pituitary adrenal insufficiency (HPAI) is controversial. Objective: Our objective was to compare standard-dose and low-dose corticotropin tests for diagnosing HPAI. Data Sources: We searched the PubMed database from 1966-2006 for studies reporting diagnostic value of standard-dose or low-dose corticotropin tests, with patient-level data obtained from original investigators. Study Selection: Eligible studies had more than 10 patients. All subjects were evaluated because of suspicion for chronic HPAI, and patient-level data were available. We excluded studies with no accepted reference standard for HPAI (insulin hypoglycemia or metyrapone test) if test subjects were in the intensive care unit or if only normal healthy subjects were used as controls. Data Extraction: We constructed receiver operator characteristic (ROC) curves using patient-level data from each study and then merged results to create summary ROC curves, adjusting for study size and cortisol assay method. Diagnostic value of tests was measured by calculating area under the ROC curve (AUC) and likelihood ratios. Data Synthesis: Patient-level data from 13 of 23 studies (57%; 679 subjects) were included in the metaanalysis. The AUC were as follows: low-dose corticotropin test, 0.92 (95% confidence interval 0.89-0.94), and standard-dose corticotropin test, 0.79 (95% confidence interval 0.74-0.84). Among patients with paired data (seven studies, 254 subjects), diagnostic value of low-dose corticotropin test was superior to standard-dose test (AUC 0.94 and 0.85, respectively; P < 0.001). Conclusions: Low-dose corticotropin test was superior to standard-dose test for diagnosing chronic HPAI, although it has technical limitations. (J Clin Endocrinol Metab 93: 4245-4253, 2008)WoSScopu