Abderrahim Bakak

Two-dimensional phosphorus–nitrogen (P–N) allotropes are emerging as promising candidates for advanced nanoelectronic and optoelectronic applications.

In view of climate change, seawater desalination is of concern to mankind, as the most difficult step in water treatment is the isolation of NaCl from seawater. The methods currently used to disable seawater remain costly, so it is important to understand and improve other methods for reducing the cost of seawater filtration. An atomic-scale computational study of NaCl and H₂O adsorption on graphite and graphene is presented, with the aim of estimating the ability of graphite-graphene to remove NaCl from seawater to obtain drinking water. The calculations are based on Density Functional Theory (DFT), using the Grid-based Projector-Augmented Wave (GPAW) approach, Atomistic Simulation Environment (ASE), and Quantum ESPRESSO methods. The main results of our work are the optimization of H₂O and NaCl molecule energies and densities of molecular states, and the calculation of the optimal adsorption distance of these molecules on the adsorbent (graphite-graphene). The observed changes in adsorption energies and density of states of the adsorbent could be exploited in the perspective of seawater filter applications. Our results could contribute to the optimization of potential seawater filter applications. The present work provides interesting information to the theoretical and experimental communities working in this field of research. It opens up the debate on the adsorption of H₂O and NaCl molecules on graphite and graphene.

Electronic and dielectric properties are essential for understanding many functional materials, predicting their behavior and optimizing their performance across different shapes, geometries and scales. Several approaches were developed and explored to investigate more or less deeply the appropriate properties. One of the most appealing, accurate and efficient approach is first principle simulations based on modern theory of polarization. Especially with the increased availability of powerful computational resources and techniques. Building upon these advancements, our contribution aims to elucidate an efficient methodology for studying electronic and dielectric properties by applying the Berry phase and Maximally Localized Wannier functions methods. Our exploration will initially focus on a systematic study of the electronic, chemical bonding, ferroelectric and piezoelectric properties of the well-known prototypical bulk system PbTiO₃. Subsequently, we will extend our study to examine slab properties as surface termination and slab thickness effect on electronic properties, utilizing the robust Wannier-justified Tight Binding model.

This paper focuses on the numerical study of spherical particle sedimentation, taking into account hydrodynamic interactions. Infinite impulse response (IIR) digital filters, specially tailored to solve the sedimentation dynamics, were used in the present study to numerically solve the coupled ordinary differential equations with the time-dependent coefficients of the problem. Hydrodynamic interactions are modeled using the Rotne–Prager–Yamakawa (RPY) approximation, to which a correction is made to better account for short-range interactions. In order to validate both the proposed numerical resolution method and the RPY correction, this paper begins with the study of two interacting spherical particle sedimentation methods. Comparisons with previously published analytical or numerical results confirm the relevance of the present approach.

We report, in this work, our study of the thermal conductivity of high-viscosity nanofluids based on glycerol. Three nanofluids have been prepared with different thermal contrasts, by suspending graphene flakes, copper oxides, or silica nanoparticles in pure glycerol. The nanofluids were thermally characterized at room temperature with the 3ω technique, with low amplitudes of the temperature oscillations. A significant enhancement of the thermal conductivity is found in both the glycerol/copper oxide and the glycerol/graphene flake nanofluids. Our results question the role played by the Brownian motion in the microscopic mechanisms of the thermal conductivity of high-viscosity glycerol-based nanofluids. A similar behavior of the thermal conductivity as a function of the nanoparticle volume fraction was found for all three glycerol-based nanofluids presently investigated. These results could be explained on the basis of fractal aggregation in the nanofluids.