El Haj Hassan

@ul.edu.lb

EDST-PRASE
Lebanese University



                 

https://researchid.co/fouadelhajhassan

Professor Fouad El Haj Hassan received the Ph.D. degree in 2000 in condensed matter Physics, from Metz University, France. He joined Lebanese University-Faculty of sciences (I) in 2001, where he is currently a Professor of Physics and condensed matter. Prof. El Haj Hassan is the director of Platform for research and analysis in Environmental Sciences (PRASE – EDST - UL) since October 2015. Coordinator of the Faculty of sciences 4 - annex Baalbek between 2009 and 2013.
Prof. El Haj Hassan is a holder of a Lebanese Research Chair in computational Physics; he is founder and TPC of several international conferences such as the MEDGREEN-LB 2011, ICM2013 IEEE, ICM2015 IEE and ICM2021 IEE. He is plenary speaker in many international conferences and editor board of "Condensed matter physics" and "the scientific world journal". He is referee for more than 12 international journals. Prof El Haj Hassan published 117 peer reviewed journal papers with about 1917 citations and one book chapter. He

EDUCATION

PhD Material sciences

123

Scopus Publications

Scopus Publications

  • First-principles insights into niobate-tantalate double perovskites (K2NbTaO6 and Rb2NbTaO6) for green energy applications
    Ouendadji Salima, Aissani Ali, El Haj Hassan Fouad, Benahmedi Lakhdar, Aouati Redha, and Djaaboube Halima

    Elsevier BV


  • Optothermal Raman analysis of thermal conductance and boundary resistance in a subwavelength single nanoparticle
    Nourhan Barakat, Fouad El Haj Hassan, and Michel Kazan

    AIP Publishing
    We present optothermal Raman spectroscopy as a powerful technique for characterizing the thermal properties of individual subwavelength nanoparticles. This method enables the extraction of the intrinsic thermal conductance of an individual nanoparticle with an average size representative of the inclusion population and the thermal resistance at the interface between the nanoparticle and its surrounding matrix. By overcoming the spatial resolution limitations of conventional techniques, such as scanning thermal microscopy, and eliminating the need for complex nanoscale heat transfer modeling, optothermal Raman spectroscopy provides direct, size-independent measurements with high accuracy. The technique involves measuring the thermal conductance of target nanoparticles embedded in a matrix of smaller, low-density particles at varying mass fractions. These measurements are then fitted to the effective medium theory to extract both the intrinsic thermal conductance and boundary thermal resistance of the nanoparticles. Validation studies were conducted on monoclinic gallium oxide (β-Ga₂O₃, 590 nm) and zinc oxide (ZnO, 500 nm) particles in a granular silicon matrix, as well as silicon (Si, 100 nm) nanoparticles in a granular carbon matrix. The β-Ga₂O₃ and ZnO particles, with bulk-like thermal properties, served as benchmarks, while the Si nanoparticles exhibited size-dependent thermal behavior. Measurements relied on the resonance frequency of Si as a precise thermometric signal, and results were corroborated by first-principles calculations. By providing direct, reliable measurements without intricate modeling, optothermal Raman spectroscopy offers significant advantages for thermal property characterization. This versatile technique holds great promise for advancing research in materials science and nanotechnology.

  • Theoretical investigation of the thermal conductivity of Ga<inf>2</inf>O<inf>3</inf> polymorphs
    Fatima Safieddine, Fouad El Haj Hassan, and Michel Kazan

    Elsevier BV

  • Thermal properties of In<inf>2</inf>O<inf>3</inf> and α-Ga<inf>2</inf>S<inf>3</inf> compounds
    Fatima Safieddine, Fouad El Haj Hassan, and Michel Kazan

    Elsevier BV

  • Ultralow thermal conductivity in Si-Ge nanograin mixtures: A cost-effective granular material for thermoelectric applications
    Nourhan Barakat, A. Akkoush, Fouad El Haj Hassan, and Michel Kazan

    AIP Publishing
    This paper presents a theoretical study of the thermal conductivity of Si–Ge nanograin mixtures using a multiscale computational methodology based on solving the Boltzmann transport equation for phonons with first-principles techniques. A size-dependent correction factor is developed to account for the spatial dependence of the phonon distribution function on nanograin size, with parameters derived from the phonon properties of infinite Si and Ge crystals. This approach makes it possible to accurately calculate the thermal conductivity within a single nanograin, using force constants obtained from first-principles calculations. Thermal energy transport by phonons across grain boundaries is modeled by accounting for phonon transmission by two-phonon processes, weighting specular, and diffuse transmission for each phonon mode as a function of the root-mean-square roughness of the boundary relative to the phonon wavelength. The boundary thermal conductance model, previously validated against experimental data, is implemented using first-principles techniques. This approach excludes specular transmission for phonon modes with specific symmetries while ensuring conservation of the total number of modes in each symmetry class. The study examines the influence of grain size, nanograin mixture composition, temperature, and boundary asperities on the thermal conductivity of nanograin mixtures.

  • Modification of the Acoustic Mismatch Model and Diffuse Mismatch Model for Accurate Prediction of Interface Thermal Conductance at Low Temperatures
    Nourhan Barakat, Fouad El Haj Hassan, and Michel Kazan

    ASME International
    Abstract Houston's method for summing phonon modes in the Brillouin zone is applied to exclude specular transmission of phonon modes of specific symmetries, thus, modifying the Acoustic Mismatch Model when phonon heat flux is incident from a heavier to a lighter medium. The Houston method is also used to impose conservation of the number of phonons in each direction of high-symmetry, thus modifying the detailed balance theorem and the Diffuse Mismatch Model. Based on the assumption that phonons are in equilibrium at the interface and are transmitted specularly or diffusely by two-phonon elastic processes, interpolation between the modified Acoustic Mismatch Model and the modified Diffuse Mismatch Model has led to a general analytical formalism for low-temperature interface thermal conductance. The Debye temperature, the only parameter in the derived formalism, is expressed as a function of temperature by assimilating numerically obtained specific heat values to the Debye expression for specific heat. Previous measurements of the low-temperature thermal conductance of smooth and rough interfaces between dissimilar materials could be reproduced numerically without adjustment of model parameters, demonstrating the importance of modifications to the Acoustic Mismatch Model and the Diffuse Mismatch Model and supporting the hypothesis that anharmonic processes play a minimal role in heat transport across the interfaces studied below room temperature. The formalism developed is used to study the thermal conductance of the interface between silicon and germanium because of the potential of silicon-germanium nanocomposites for thermoelectric applications.

  • Comparative study of the fundamental properties of Ga<inf>2</inf>O<inf>3</inf> polymorphs
    Fatima Safieddine, Fouad El Haj Hassan, and Michel Kazan

    Elsevier BV

  • Ab-initio study of the electronic structure of LaF including spin–orbit coupling
    Joumana Assaf, Rima Assaf, and Fouad El Haj Hassan

    Springer Science and Business Media LLC

  • Electrical conductivity and impedance calculated beyond τ-approximation
    Farraj Maallawi and Fouad El Haj Hassan

    Springer Science and Business Media LLC
    In the present work, we include the electrons that penetrate the skin layer by seeing their effects on electrical conductivity and metal impedance in both cases of normal and anomalous skin effects. The τ-approximation is used in order to derive new formulas for the electrical conductivity and surface impedance of the normal metal based on the new form of Boltzmann’s kinetic equation.

  • Tuning the hybrid borophene−/graphene-ionic liquid interface: Effect of metal cations on the electronic and photonic properties
    Kazem Zhour, José M. Otero-Mato, Fouad El Haj Hassan, Hussein Fahs, Majid Vaezzadeh, E. López-Lago, Luis J. Gallego, and Luis M. Varela

    Elsevier BV
    Abstract A density functional theory study of the effect of the adsorption of a mixture of potassium salt and an imidazolium-based ionic liquid on the electronic and optical properties of graphene and borophene is performed. This addition leads to a downward shift of the Dirac cone for both structures due to the electron transferred from potassium to the graphene and borophene sheets. The transferred charge to the wall and the binding energy of potassium are bigger than in the case of the adsorption of potassium on pristine graphene. The Bader analysis shows that the presence of potassium makes the charge distributions in graphene and the layers of boron atoms in borophene more homogenous and the electronic distribution in the sheets is consequently less affected by the electromagnetic interaction with the ions in the mixture. Moreover, the results show that the optical properties are altered by the metallic cation, especially at low frequencies where ionic liquid-enhanced 2D plasmons are registered due to the doping of 2D sheets by electrons transferred from the potassium atoms leading to near zero values of the parallel components of the dielectric function and refractive index.

  • Water-silanol interactions on the amorphous silica surface: A dispersion-corrected DFT investigation
    Youssef Berro, Michael Badawi, Fouad El Haj Hassan, Mounir Kassir, and Frederik Tielens

    Elsevier BV
    Abstract Interpreting the interaction between the amorphous silica surface and water is a key step to understand its physicochemical properties. However, due to the flexibility of the structure and the distribution of types and geometries of the silanols one can obtain a broad range of interaction energies, as was already shown in former studies. This time we were able to investigate the distribution of silanols in relation with the calculated interaction energies, and thus designate those different silanols sites. Different dispersion-correction PBE-D (PBE + D2, D3, D3-BJ, TS, TS-HI, MBD, and FI-MBD) and meta-GGA SCAN methods has been used to quantify the interactions between water and defined silanols sites of the surface. All the methods give similar interaction energies, showing equivalent performances of SCAN and PBE-D methods to describe week interactions in our system. Following various routes, we identified a protocol of calculation in order to compute the interaction energies more accurately, taking into consideration the van der Waals (vdW) forces. Once different silanols are correctly described within the calculation level, it is clear that the geometry and environment determine its chemistry. Furthermore, the possible deformation of the silica surface affected by the water interaction is studied. The quantification of the interaction energies is important in order to correctly scale the results and confront with the experiments. With this information in mind, one can think about synthesis techniques that modify the silanols distribution of the silica surface in a way to tune its hydrophobicity and acidity.

  • Ab-initio study of ordered III–V antimony-based semiconductor alloys GaP<inf>1</inf><inf>-</inf><inf>x</inf>Sb<inf>x</inf>andAlP<inf>1</inf><inf>-</inf><inf>x</inf>Sb<inf>x</inf>
    F Annane, H Meradji, S Ghemid, H Bendjeddou, F El Haj Hassan, Vipul Srivastava, and R Khenata

    Springer Science and Business Media LLC
    In this work, we have investigated the structural, electronic and thermodynamic properties of GaP $$_{1-x}$$ Sb $$_{x}$$ and AlP $$_{1-x}$$ Sb $$_{x}$$ ternary alloys for a number of ordered structures and compositions in a series of first-principles calculations within the density functional theory, using full potential-linearised augmented plane-wave (FP-LAPW) method, as implemented in the WIEN2k code. The exchange-correlation effect was treated within the generalised gradient approximation (GGA) in the form of GGA-PBEsol to optimise the structure and to compute the ground-state properties. In addition to the GGA, the modified Becke–Johnson (mBJ) potential coupled with the spin-orbit interaction (SOI) was also applied to obtain reliable results for the electronic properties. Our investigation on the effect of composition on lattice constant, bulk modulus and band gap showed almost nonlinear dependence on the composition. The GaP $$_{1-x}$$ Sb $$_{x}$$ and AlP $$_{1-x}$$ Sb $$_{x}$$ alloys are found to be semiconductors with a positive energy gap for the whole concentration range. The spin-orbit splitting $$\\Delta _{\\mathrm {SO}}$$ was found to increase with Sb composition with a marginal bowing parameter. Besides, a regular-solution model was used to investigate the thermodynamic stability of the alloys which mainly indicates a phase miscibility gap. In addition, the quasiharmonic Debye model was applied to analyse the effect of temperature and pressure on the Debye temperature and heat capacity.

  • Physical and dielectric properties of (Bi,Pb)-2223 superconducting samples added with BaFe<inf>12</inf>O<inf>19</inf> nanoparticles
    Khulud Habanjar, F. El Haj Hassan, and R. Awad

    Elsevier BV
    Abstract Co-precipitation and solid-state reaction techniques were used to synthesize BaFe12O19 nanoparticles and (BaFe12O19)x(Bi,Pb)-2223 superconducting samples, with 0.00 ≤ x(wt%) ≤ 1.5, respectively. Hard ferromagnetic BaFe12O19 nanoparticles had hexagonal structure with an average size of 63 nm. The structure of the superconducting samples reveal that the added nanoparticles settled at the grain boundaries without altering the host structure superconductors. The elemental composition of the samples is investigated using proton induced X-ray emission. The superconducting transition temperature (Tc) and the critical current density (Jc) were enhanced up to x = 0.5 wt%. The maximum values of dielectric properties of (BaFe12O19)x(Bi,Pb)-2223 were found at lower frequencies and higher temperatures.

  • Electronic and optical properties of borophene and graphene with an adsorbed ionic liquid: A density functional theory study
    Kazem Zhour, José M. Otero-Mato, Fouad El Haj Hassan, Hussein Fahs, Majid Vaezzadeh, E. López-Lago, Luis J. Gallego, and Luis M. Varela

    Elsevier BV
    Abstract We present a comparative density functional theory study of the electronic and optical properties of graphene and borophene with an adsorbed ionic liquid. The Dirac cones of these two-dimensional nanostructures are not affected by the presence of the ionic liquid close to these sheets, not even in the borophene one in which a very small charge transfer to the ionic liquid anion is detected. However, Bader analysis and charge density calculations showed that the polarization of the ionic liquid induces a redistribution of the electric charge in both sheets as a consequence of the electromagnetic interaction between the anion and cation of the ionic liquid and the electrons on the two-dimensional materials, the effect being notably stronger in graphene than in borophene. Our calculations reveal that several changes take place in the dielectric constant and electron energy loss spectra, including shifts and damping of plasmon bands, related to electrostatically induced changes in the adsorbent surface electron charge distributions and to plasmon loss channels associated to excitations of electrons in the energy levels of the adsorbed ionic liquid species close to the Fermi level of the surface material. While only minor changes are registered in borophene plasmon spectra and in the IR and visible regions of the graphene spectra, important changes in the graphene ultraviolet C and X-ray spectra are registered due to the existence of IL electronic energy levels close to the Fermi level of graphene that are absent in borophene.

  • Imprinting isolated single iron atoms onto mesoporous silica by templating with metallosurfactants
    Y. Berro, S. Gueddida, Y. Bouizi, C. Bellouard, El-E. Bendeif, A. Gansmuller, A. Celzard, V. Fierro, D. Ihiawakrim, O. Ersen,et al.

    Elsevier BV
    HYPOTHESIS One of the main drawbacks of metal-supported materials, traditionally prepared by the impregnation of metal salts onto pre-synthesized porous supports, is the formation of large and unevenly dispersed particles. Generally, the larger are the particles, the lower is the number of catalytic sites. Maximum atom exposure can be reached within single-atom materials, which appear therefore as the next generation of porous catalysts. EXPERIMENTS Herein, we designed single iron atom-supported silica materials through sol-gel hydrothermal treatment using mixtures of a non-ionic surfactant (Pluronic P123) and a metallosurfactant (cetyltrimethylammoniumtrichloromonobromoferrate, CTAF) as porogens. The ratio between the Pluronic P123 and the CTAF enables to control the silica structural and textural properties. More importantly, CTAF acts as an iron source, which amount could be simply tuned by varying the non-ionic/metallo surfactants molar ratio. FINDINGS The fine distribution of iron atoms onto the silica mesopores results from the iron distribution within the mixed micelles, which serve as templates for the polymerization of the silica matrix. Several characterization methods were used to determine the structural and textural properties of the silica material (XRD, N2 sorption isotherms and TEM) and the homogeneous distribution and lack of clustering of iron atoms in the resulting materials (elemental analysis, magnetic measurements, pair distribution function (PDF), MAS-NMR and TEM mapping). The oxidation and spin state of single-iron atoms determined from their magnetic properties were confirmed by DFT calculations. This strategy might find straightforward applications in preparing versatile single atom catalysts, with improved efficiency compared to nanosized ones.

  • Skyrmion based random bit generator
    Israa Medlej, Abbass Hamadeh, and Fouad El Haj Hassan

    Elsevier BV
    Abstract Magnetic skyrmions are topologically quasi-particles offering a wide range of applications ranging from memory to oscillator and neuromorphic elements such as neurons and synapses. However, their trajectory driven by currents exhibits the so-called skyrmion Hall angle that is a limiting factor for the above-mentioned applications. Here, we study the stochastic dynamics of synthetic antiferromagnetic skyrmions driven by the spin-Hall effect in a racetrack memory with bifurcation. We show the limit of their application in programmable logic and a possible direction to use this design as a skyrmion based random bit generator.

  • First-principles investigation of the structural, elastic, electronic, and optical properties of semiconducting AgBr<inf>1–</inf><inf>x</inf>i<inf>x</inf>(0 ≤ x ≤ 1) ternary alloys in rock-salt and zinc blende structures
    H. Rekab-Djabri, Mohamed Drief, Manal M. Abdus Salam, Salah Daoud, F. El Haj Hassan, and S. Louhibi-Fasla

    Canadian Science Publishing
    In this work, first principle calculations of the structural, electronic, elastic, and optical properties of novel AgBr1–xIx ternary alloys in rock-salt (B1) and zinc-blende (B3) structures are presented. The calculations were performed using the full-potential linear muffin-tin orbital (FP-LMTO) method within the framework of the density functional theory (DFT). The exchange and correlation potentials were treated according to the local density approximation (LDA). The lattice constants for the B1 and B3 phases versus iodide concentration (x) were found to deviate slightly from the linear relationship of Vegard’s law. The calculated electronic properties showed that AgBr1–xIx alloys in the B3 structure have a direct band gap (Γ – Γ) for all concentrations of x, which means that they can be used in long-wavelength optoelectronic applications, while in the B1 structure they have an indirect (Γ – R) band gap. The elastic constants Cij, shear modulus G, Young’s modulus E, Poisson’s ratio ν, index of ductility B/G, sound velocities vt, vl, and vm, and Debye temperature θD were also reported and analyzed. By incorporating the basic optical properties, we discussed the dielectric function, refractive index, optical reflectivity, absorption coefficient, and optical conductivity in terms of incident photon energy up to 13.5 eV. The present results were found to be in good agreement with the available experimental and other theoretical results.

  • First-principles calculations to investigate half-metallic ferromagnetism in Zn<inf>0.50</inf>Ti<inf>0.50</inf>S alloy by using DFT + U calculations
    Aicha Bahnes, Mohammed El Amine Monir, Younes Mouchaal, Fouad El Haj Hassan, Zohra Bahnes, and Abdelkarim Bendoukha Reguig

    Informa UK Limited
    ABSTRACT The spin-polarized structural, electronic and magnetic properties of the Ti-doped zincblende ZnS compound at x = 0.50 (Zn0.50Ti0.50S alloy) have been investigated by employing the first-principles full-potential linearised augmented plane wave with local orbitals (FP-L/APW + lo) method within the frame-work of spin-polarized density functional theory (spin-DFT). For the treating of the structural properties, the electronic exchange and correlation (XC) functional was defined by generalised gradient approximation (GGA), whereas both GGA and GGA + U approximations are applied to treat and to compare the electronic and magnetic properties (U is the Coulomb repulsion energy). It has been confirmed that the ferromagnetic (FM) state of this alloy is found the most stable phase; however, all the equilibrium lattice parameters such as; lattice constant (a0), bulk modulus (B0), and its first-pressure derivative (B′) are computed in all paramagnetic, ferromagnetic and anti-ferromagnetic phases. The calculations of electronic properties unveil the perfect half-metallic character in the tetragonal Zn0.50Ti0.50S system. The computed magnetic properties reveal that the total magnetic moment is mainly originated from the transition element (TM) of Ti. Moreover, we have found that the p-d hybridisation is the paramount responsible for the reduction of the magnetic moment of TM from its free space charge value and for the production of minor magnetic moments on the nonmagnetic Zn and S sites.

  • Ab initio study of the adsorption of Potassium on B, N, and BN-doped graphene heterostructure
    Kazem Zhour, Fouad El Haj Hassan, Hussein Fahs, and Majid Vaezzadeh

    Elsevier BV
    Abstract The adsorption of Potassium atom on graphene doped with Nitride, Boron, and Boron nitride hexagons is studied using DFT with LDA and GGA for both spin and non-spin polarization calculations. The distortion in graphene resulting from Boron nitride doping is unnoticeable; alternatively, pure Boron and Nitrogen hexagons introduce high level of distortion in the layer. Adsorption energy, structural geometry, density of state, band structure, charge density, charge transfer, dipole moment and work function are calculated. For Boron and Nitrogen hexagons-doped graphene, the adsorption energy of Potassium increases dramatically compared to pristine graphene, but in the case of Boron nitride hexagons, calculations show weak adsorption energy of Potassium on the doped sheet. The doping of graphene with Boron nitride opens a small band gap, and the adsorption of Potassium rises the Fermi level above the opened gap leading to the formation of n-type semiconductor. Co-existence of partial covalent bond and ionic bond between Potassium and the doped graphene has been demonstrated. The transfer of charges is calculated in four different methods, one by using Bader analysis and the other three are based on DOS, average charge density difference and electric dipole moment.

  • Atomistic description of phenol, CO and H<inf>2</inf>O adsorption over crystalline and amorphous silica surfaces for hydrodeoxygenation applications
    Youssef Berro, Saber Gueddida, Sébastien Lebègue, Andreea Pasc, Nadia Canilho, Mounir Kassir, Fouad El Haj Hassan, and Michael Badawi

    Elsevier BV
    Abstract The upgrading of lignin-derived bio-oils involves a HydroDeOxygenation (HDO) reaction through either the Hydrogenation (Hyd) or the Direct DeOxygenation (DDO) route, the latter limiting hydrogen consumption. Herein, dispersion-corrected DFT has been used to evaluate the adsorption behavior of phenol (as a representative model of bio-oils) and two by-products (water and CO) over various crystalline and amorphous silica surfaces to evaluate their potential selectivity (DDO/Hyd) and efficiency (low inhibiting effect) for HDO processing. Phenol can adsorb through three modes, flat π-interaction, flat O-interaction or perpendicular O-interaction. All crystalline surfaces show a preference for the flat π-interaction, which is expected to promote the Hyd route. Over amorphous surfaces the flat O-interaction dominates, and a very specific and strong interaction (around −120 kJ/mol) was found on SiO2-3.3 and SiO2-2.0 surfaces where the phenol molecule loses its aromaticity, which is very promising for its degradation under catalytic conditions. In addition, this makes those surfaces very efficient to adsorb selectively phenol in presence of water and CO. Remarkably, on all silica surfaces, the interaction energy of CO is nearly negligible, which makes them more attractive for HDO process compared to sulfide catalysts with respect to the inhibiting effect criteria.

  • Vickers Microhardness Studies for SmBa<inf>2</inf>Cu<inf>3</inf>O<inf>7-δ</inf> Added with NiO Nanosized Particles
    S. Rmeid, H. Basma, M. Roumie, F. Elhaj Hassan, and R. Awad

    Springer Science and Business Media LLC
    The effect of nanosized particles NiO addition on the Vickers microhardness of polycrystalline SmBa2Cu3O7-δ was investigated. Various amounts of nanosized particles NiO (x = 0.00, 0.02, 0.04, 0.08, and 0.12 wt%) were added to SmBa2Cu3O7-δ prepared by the solid-state reaction method. Sample characterizations were carried out using X-ray powder diffraction (XRD), particle induced X-ray emission (PIXE), Rutherford backscattering (RBS), and scanning electron microscopy (SEM). The nanosized particle addition does not influence the orthorhombic structure of SmBa2Cu3O7-δ, whereas it affects the oxygen content δ. The electrical and mechanical properties of (NiO)xSmBa2Cu3O7-δ samples were measured using four-standard probe technique and Vickers microhardness in order to investigate the effect of NiO nanosized particles on superconducting transition temperature and Vickers microhardness number Hv. The Vickers microhardness data were analyzed using Hays and Kendall (HK), elastic plastic deformation (EPD), and modified proportional specimen resistance (MPSR) models. The analysis showed that the MPSR model was found to be the best to describe the behavior of Hv.

  • Fundamental properties of scandium chalcogenides and their alloys: DFT study
    A. A. Ahmad, S. Mahmoud, B. Alshafaay, R. Halabi, and F. El Haj Hassan

    Springer Science and Business Media LLC
    AbstractThe full-potential linearized-augmented plane wave calculations based on density functional theory are performed to study the structural, electronic, optical and thermodynamic properties of scandium chalcogenides ScX (X = S, Se, Te) and their ternary alloys at equilibrium as well as under pressure. The revised Perdew–Burke–Ernzerhof generalized gradient approximation (GGA) is used to calculate the structural properties. The electronic and optical properties are calculated employing the GGA and the modified Becke–Johnson (mBJ) approaches. Moreover, the calculated lattice parameters agree well with the experiment results. The structure NaCl-type (B1) of the scandium chalcogenides undergoes under pressure a structural phase transition to CsCl-type (B2) and ZnS-type (B3). The binary and ternary alloys indicate a metallic behavior using GGA and mBJ scheme. The interband contribution to the optical properties is investigated by calculating the dielectric parameters ε1(ω), ε2(ω) and the index of refraction n(ω). A quasi-harmonic Debye model is applied to calculate the thermal properties.

  • ab-initio investigations of electronic and magnetic properties of the tetragonal chalcopyrite BeTiTe<inf>2</inf> compound: DFT + U study
    Mohammed El Amine Monir, Fouad El Haj Hassan, Aicha Bahnes, Hadj Baltach, and Abdelkarim Bendoukha Reguig

    Informa UK Limited
    ABSTRACT The spin-polarised structural, electronic, and magnetic properties of the chalcopyrite BeTiTe2 compound in tetragonal structure (Be0.50Ti0.50Te) have been studied by employing first-principles full-potential linearised augmented plane wave plus local orbitals (FP-L/APW + lo) method within the density functional theory (DFT) and implemented in WIEN2k code. The exchange and correlation energy are described in two frameworks of GGA (generalised gradient approximation) and GGA + U (U is the Hubbard term). The structural analysis confirms that the ferromagnetic phase of the tetragonal BeTiTe2 compound (Be0.50Ti0.50Te) is energetically more favourable; also different equilibrium lattice parameters, such as lattice constants (a0 and c0), bulk modulus (B0), and its first-pressure derivative (Bʹ) have been evaluated in both paramagnetic and ferromagnetic phases. The electronic results of the tetragonal BeTiTe2 compound show a complete half-metallic behaviour. Moreover, the computed total magnetic moment of this compound is close to 4 μB, confirming its half-metallic ferromagnetic nature.

  • Ab initio study of the fundamental properties of Zn <inf>1</inf><inf>-</inf><inf>x</inf>TM <inf>x</inf>Se (TM = Mn, Co and Fe)
    F Soltani, H Baaziz, Z Charifi, F El Haj Hassan, and B Hamad

    Springer Science and Business Media LLC
    The structural, electronic, magnetic, thermal and elastic properties of Zn$$_{1-x}$$1-xTM$$_{x}$$xSe (TM $$=$$= Mn, Co and Fe) ternary alloys are investigated at x = 0, 0.25, 0.50, 0.75 and 1.00 in the zincblende (B3) phase. The calculations are performed using all-electron full-potential linearised augmented plane-wave (FP-LAPW) method within the framework of the density functional theory (DFT) and the generalised gradient approximation (GGA). The electronic and magnetic properties were performed using the modified Becke–Johnson potential combined with the GGA correlation (mBJ-GGA). The electronic structures are found to exhibit a semiconducting behaviour for Zn$$_{1-x}$$1-xMn$$_{x}$$xSe and Zn$$_{1-x}$$1-xCo$$_{x}$$xSe and a half-metallic behaviour for Zn$$_{1-x}$$1-xFe$$_{x}$$xSe alloys at all concentrations, while CoSe with $$x = 1.00$$x=1.00 is found to exhibit a metallic behaviour. The calculated magnetic moment per substituted transition metal (TM) Mn, Co and Fe atoms for half-metallic compounds are found to be 2.5, 1.5 and 2 $$\\mu $$μ$$_{\\mathrm{B}}$$B, respectively. The p–d hybridisation between the TM d- and Se p-states reduces the local magnetic moment of Mn, Co and Fe and induces small local magnetic moments on Zn and Se sites. In addition, we discuss the mechanical behaviour of binary and ternary compounds and all compounds studied here are mechanically stable.

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