Iron oxides are abundant and inexpensive materials with promising potential for catalysis. However, the influence of their intrinsic magnetic properties on their catalytic activity is not well established. This study investigates the correlation of magnetic order to the catalytic activity of the α-Fe2O3 (0001) surface using the adsorption of molecular oxygen as a descriptor. Our findings reveal that the magnetic order strongly influences the O2 adsorption, yielding lower binding energies for the antiferromagnetic (AFM) configurations and making them more inert than the ferromagnetic (FM) one. We find the origin of the higher reactivity of the FM configuration in its broader d-band and its delocalization of the charge, together with the larger surface magnetization, relative to the AFM ones. Adsorption on the FM surface results in a markedly higher charge transfer to O2 than on the AFM surfaces. These results highlight the critical role of magnetic configurations in governing the adsorption and catalytic properties of α-Fe2O3 (0001) surfaces, providing valuable insights for designing and optimizing more efficient magnetic catalysts. We also investigated the adsorption energy as a function of biaxial strain, finding that compressive strain strengthens adsorption on both FM and AFM surfaces, with the FM surface gaining additional stability relative to the AFM surface under compressive strain.

A semi-empirical model was developed to reproduce ab initio excitation energies and UV–Vis absorption spectra for nanoclusters. The ZINDO/s Hamiltonian was parameterized using vertical excitation energies from EOM-CCSD for sulphur, zinc and cadmium diatomics. The newly obtained Hamiltonian, oeINDO, reproduced EOM-CCSD excitation energies with mean absolute error (MAE) of only 0.30 eV for clusters of sulphur, zinc, cadmium and their complexes. For larger clusters, oeINDO reproduced TDDFT excitation energies within MAE 0.33 eV. The calculated oeINDO UV–Vis absorption spectra agree well with EOM-CCSD and TDDFT spectra. The model was used to predict the absorption spectra of nano-sized zinc, cadmium, and sulphur and their complexes, showing that some cluster sizes may be suitable for solar cell applications.

The 1,2-dearomatized pyridine derivatives are among the most beneficial scaffolds for synthetic and medicinal chemistry and have along with others substantially contributed to pharmaceutical research. We report uncatalyzed thiocyanate-induced N-activation and nucleophilic 1,2-dearomatization of pyridinedicarbonyl dichloride with further addition of diphenylamine leading to the novel 1,2-dihydropyridine-based heterocyclic compound; ( ±) 2′-(diphenylamino)-3-thioxo-2,3-dihydro-1H,4′H-spiro[imidazo[1,5-a]pyridine-5,5′-thiazole]-1,4′-dione (1). The previously reported dearomatizations of pyridine and its derivatives usually demand a specific catalyst. Therefore, uncatalyzed 1,2-dearomatization of pyridinedicarbonyl dichloride observed in this study is unusual. Heterocyclic compound 1 will act as potential mother reagent for the synthetic route to a variety of novel heterocyclic compounds derivative to 1,2-dihydropyridine. The purity of the product was assessed by Ultraperformance Liquid Chromatography (UPLC), and the structural characterization was achieved by 1H NMR, 13C NMR, DEPT-135-NMR, IR, Liquid Chromatography Mass Spectrometry (ESI–MS), single crystal X-ray crystallography and density function theory (DFT). The reaction of pyridine-2,6-dicarbonyl dichloride with potassium thiocyanate (KSCN) and diphenylamine in acetone led to the novel heterocyclic compound typically (±) 2′-(diphenylamino)-3-thioxo-2,3-dihydro-1H,4′H-spiro[imidazo[1,5-a]pyridine-5,5′-thiazole]-1,4′-dione.

This paper examines the effects of hydroxyapatite (HA) and bone-particle (BP) doping on the removal of fluoride and bacteria by ceramic water filters (CWFs). The CWFs were produced by mixing clay, sieved sawdust, and either HA or BPs in a weight ratio of 30:50:20 and sintered at 850 degrees C or 900 degrees C to produce micro-/nano-porous structures that remove microbial pathogens (by geometric occlusion) and fluoride (by adsorption) from contaminated water. The HA-doped filters exhibited similar flow characteristics to the BP-doped filters. However, BP-doped CWFs were more effective in removing fluoride and microbial pathogens (such as E. coli) from contaminated water than HA-doped filters. The water flow rates and fluoride removal depended on sintering temperature, with CWFs sintered at 850 degrees C enabling faster flow rates of 2.2Lh(-1) and higher fluoride removal of 2.74 mol.cm(-2) than the CWFs sintered at 900 degrees C. Fluoride removal by the HA- and BP-doped filters was well characterized by Freundlich isotherms that reveal the occurrence of spontaneous but heterogeneous adsorption. The implications of the results are discussed for the design of point-of-use CWFs for the removal of fluoride and microbial pathogens.

Apolar molecules in the gas phase have no dipole moments. However, when placed in an aqueous environment, they acquire a dipole moment induced by the electric fields of the surrounding water molecules. Could these induced dipole moments, not present in the gas phase but present in solution, play an important role in the hydrophobic interaction between two apolar molecules? In particular, for two methane molecules, our results show that the interaction between the induced-dipole moments only very weakly plays a role in the aggregation of a pair of methane molecules in water. The induced-dipole-induced-dipole interaction has a magnitude as large as 1 kcal/mol for certain mutual orientations of the induced dipole moments, which is larger than the magnitude of the free energy of aggregation of the methane solutes in water. However, when averaged over all physically occurring conformations for a fixed intersolute separation, this interaction averages to an insignificant value (magnitude less than 0.01 kcal/mol) except, possibly, for some very short intermolecular separation.

This paper presents the results of a combined experimental and theoretical study of the effects of sintering temperature on the mechanical and filtration properties of clay ceramic water filters (CWFs). CWFs produced from 50:50 volume proportion mixtures of clay and sieved sawdust (porogen) were sintered at 850 degrees C, 900 degrees C and 950 degrees C to produce micro- and nano-porous structures. The sintered clay structures were then characterized using X-ray diffraction and scanning electron microscopy. The flow and filtration characteristics of the filters were then elucidated using a combination of theory and fluid flow experiments, before exploring the effects of porosity on E. coli removal and flow rates through the filter. The E. coli removal efficiency is shown to be inversely proportional to the sintering temperature, with log removal values (LRV) of 4.89, 4.59 and 4.46 for the CWFs sintered at 850 degrees C, 900 degrees C and 950 degrees C, respectively. The paper also examines the effects of sintering temperature on the compressive and flexural strengths, as well as the fracture toughness of the CWFs. The compressive strengths of the CWFs increased (between 6.55 and 7.02 MPa), whereas the flexural strengths (between 3.05 and 2.22 MPa) and the fracture toughness values (between 0.21 and 0.14 MPa root m) both decreased in response to the increased porosities induced by the increased sintering temperature. The underlying fracture and toughening mechanisms are then elucidated before discussing the implications of the results for the fabrication, transportation, and handling of robust ceramic water filters.

We report electronic band structure calculations for Sr_4Ru_3O_10 that displays both ferromagnetic and metamagnetic behavior. The density functional calculations find the ground state to be ferromagnetic in agreement with the experiment and we find that the inclusion of Coulomb Hubbard interaction U applied to the Ru 4d states has dramatic effects on the Fermi surface, which reveal the role of Coulomb interactions and correlated many-body physics. The minority spin bands are mainly empty with Fermi surfaces in the outer areas of the Brillouin zone away from the Γ point with bands that disperse steeply upward. The majority spin bands are full or nearly fully occupied and form narrow bands near the Fermi energy around the Γ point, which could be the electronic origin of the metamagnetism. The results are in qualitative agreement with recent angle resolved photoemission spectroscopy (ARPES) experiments and show the need for a combined theoretical study and experimental ARPES investigation with better energy resolution to reveal the nature of the narrow bands close to the Fermi-level, which is critical for understanding the exotic magnetic properties observed in this material.

The van der Waals heterostructure of Janus materials with a TMD monolayer was used to create a two-dimensional class of nanomaterials for photovoltaic solar cell applications. It is one of the potential methods for enhancing the performance of photovoltaic systems. Two monolayers of different 2D materials, Janus (ZrXO) and TMDs (MX2), are stacked together to form the heterojunction. Based on density functional theory structural, electrical, and optical properties were investigated. The favorable stacking and stability of the MX2/ZrXO (M = W, Mo and X = S, Se) van der Waals heterostructures are confirmed through binding energies, phonon dispersion and ab initio molecular dynamics calculations. Standard excitonic peaks, which correspond to the bound valence-band hole and conduction-band electron, as well as excitonic peaks involving the mid-gap charges, can be seen in the system's computed absorption spectrum. MX2/ZrXO van der Waals heterostructures are excellent photovoltaic candidates with a maximum achived power conversion efficiency of above 22%. Furthermore, we discovered that the heterostructure materials have a high absorption efficiency which is good for the intended photovoltaic solar cell application.

Africa tends to be isolated and sometimes forgotten when it comes to scientific research and in particular physics. But the region has great potential, being home to the youngest population in the world, and despite a variety of issues, there has been steady, albeit uneven progress towards establishing a scientific infrastructure. Ten African researchers discuss the diverse challenges and opportunities faced by physicists across the continent.

A semi-empirical Hamiltonian with the INDO approximation and CIS was parameterized to reproduce EOM-CCSD excitation energies for diatomic silicon Si-2 with different inter-atomic separations. The model Hamiltonian is transferable, producing excitation energies for clusters, Si-n (n = 3, 4, 5) with mean absolute errors (MAEs) of 0.26, 0.18, and 0.09 eV, respectively, from the EOM-CCSD energies. The absorption spectra are also in qualitative agreement with the EOM-CCSD spectra. For clusters Si-19 and Si-40, comparison with TDDFT gave MAEs of 0.32 and 0.12 eV, respectively. Predictions of excitation energies and absorption spectra are also given for Si-n (n = 124, 147, 172, 779) using the model Hamiltonian.

Molecular dynamics (MD) simulations of methane-water mixtures were performed using ab initio force fields for the CH4-H2O, H2O-H2O, and CH4-CH4 interactions. Both methane and water molecules were polarizable. From these calculations, the potential of mean force (PMF) between two methane molecules was extracted. Our results are compared with PMFs from a density-functional-theory (DFT) based Born-Oppenheimer type MD (BOMD) simulation, from a Monte Carlo (MC) simulation with ab initio-based force fields, and from MD simulations with empirical force fields. Our PMF is qualitatively similar to that obtained from the simulations with empirical force fields but differs significantly from those resulting from the DFT-BOMD and MC simulations. The depth of the PMF global minimum obtained in the present work is in a much better agreement with the experimental estimate than the result of the DFT-BOMD simulation, possibly due to the inability of DFT to describe the dispersion interactions and the lack of extensive sampling in the BOMD simulations. Our work indicates that, for a pair of methane molecules, there are configurations where the solvent increases the attraction between the solutes, but there are also conformations in which the solvent causes a weak net repulsion. On average, the methane molecules are more likely to be in the configuration where they are separated by a water molecule than in the one in which they are in contact even though the minimum of the PMF at the latter configuration is deeper than that at the former. Finally, we found that the water structure around methane solutes does not show a greater tetrahedral ordering than in neat bulk water.

In orbital-free density functional theory (OFDFT), an equation exists for $\psi = \sqrt n$, the square root of the ground state electron density $n$. We show that $\psi$ cannot be expanded as a linear combination of elements of a complete set of basis functions except in the case of one or two electron systems. This is unlike the case for the ground state of a system of identical bosons in which the square root of the ground state bosonic density can have an expansion as a linear combination of elements of a complete set of basis functions.

Solar energy is one of the primary sources of energy replacing fossil fuels due to its abundance. Its versatility and environmental friendliness has made it one of the most promising renewable sources of energy. Solar cells convert solar energy into Electrical Energy. The effort to improve the efficiency of these cells and the reduction of their costs has been a major concern for a long time. Modeling of various structures of solar cells provides an insight into the physics involved in its operation and better understanding of the ways to improve their efficiency. This work modeled Poisson Equation in 2D for an abrupt and linearly graded charge densities system with arbitrary points in space. Linear approximation and differentials, finite difference method, boundary conditions and MATLAB were used to obtain the solution. This is the first step in developing a general purpose semiconductor device simulator that is functional and modular in nature. It was observed that highest electric potential was obtained where the point charge was placed for linearly graded and doping type changed over a small distance compared to the extent of the depletion region for abrupt p-n junction. By solving Poisson equation, voltage, electric field, electric charge density and density of free carriers inside the solar cell can be known.

Estimating aerosol optical thickness (AOT) over regions can be tasking if satellite data set over such region is very scanty. Therefore a technique whose application captures real-time events is most appropriate for adequate monitoring of risk indicators. A new technique i.e. arithmetic translation of pictorial model (ATOPM) was developed. The ATOPM deals with the use mathematical expression to compute other meteorological parameters obtained from satellite or ground data set. Six locations within 335 (x) 230 Km(2) area of a selected portion of Nigeria were chosen and analyzed -using the meteorological data set (1999-2012) and MATLAB. The research affirms the use of some parameters (e.g. minimum temperature, cloud cover, relative humidity and rainfall) to estimate the aerosol optical thickness. The objective of the paper was satisfied via the use of other meteorological parameters to estimate AOT when the satellite data set over an area is scanty.

We propose that the aerosols in the atmosphere form layers of varying refractivity. In this paper, we used proven dispersion model alongside the unified number to determine the dynamics of the aerosol transport. The inability of scientist to calculate the atmospheric constant over an area has lead to frequent failures of ground measuring devices e.g. radiosonde, weather stations in developing regions is worrisome. From literatures, established projects like AERONET, AMMA e.t.c. are burdened by same challenge. At the moment, AERONET or AMMA database shows a large volume of data loss. With only about 47% data set available to scientist, it is evident that accurate nowcast or forecast cannot be guaranteed. Upon numerical simulations, it revealed that the atmospheric constant over Lagos-Nigeria is a1 = 1.175, a2 = 0.88, n1 = 0.2926 and n2 = 0.3573. Lagos lies within the latitude of 6.465°N and longitude of 3.406°E.