Publications Scientifiques

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Author: search.filters.author.Belayadi, Adel

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    Computational study of transition metal coordinated polyaniline: A first principle investigation into tuning the electronic properties of the resulting hybrid material
    (Elsevier B.V., 2024) Bouallag, Sihem; Mougari, Ahmed; Zabat, Mokhtar; Belayadi, Adel
    Tuning the electronic properties of polyaniline remains one of the most important features for the development of advanced materials in electronics. In this contribution, we use density functional theory to investigate the electronic properties of polyaniline when coordinating transition metals (Mn, Fe, Co, Cu, Zn) are embedded in the polymer structure. Importantly, the results reveal that in the presence of transition metal with high electronegativity, the coordinated polyaniline winds up with a decreased gap. Indeed, the band gap for H-PANI decreases from 0.911 eV to 0.513 eV for H-PANI-Mn (lower electronegativity) and to 0.201 eV for H-PANI-Zn (higher electronegativity). This reduction in the energy gap is attributed to enhanced electron delocalization due to increased overlap of electron wavefunctions in the hybrid structure. The results also reveal that the presence of transition metals lead to lower the chemical hardness from 3.252 eV in the case of H-PANI into 0.256 eV for H-PANI-Mn and 0.100 eV for H-PANI-Zn. Additionally, the results from molecular electrostatic potential highlight that PANI-Transition metal sustains more delocalization of charge density distribution compared to H-PANI, leading to molecule polarization which does play a crucial role in various chemical phenomena. These later reveal that the electron density polarization in polyaniline can interestingly be controlled through doping and coordinating the polymer structure with additional transition metals. Therefore, the obtained results might be used in the optimization of electrochemical charge storage in supercapacitors.
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    Computing the surface electronic states on the (100), (110) and (111) surfaces of FCC monatomic crystals
    (World Scientific Publishing, 2021) Bourahla, Boualem; Belayadi, Adel
    In this study, we carry out a simulation of the surface band structures for face-centered cubic (fcc) leads that end up in (100), (110) and (111) surfaces. The surface Hamiltonian matrix is constructed from tight-binding approach and the secular equations of the surface eigenvalue problem. The solution of the problem is performed by integrating the Landauer–Büttiker formalism (LBF) in the phase field matching approach (PFMA). The LBF provides the quantum scattering properties and the PFMA connects the bulk modes to those of the surface based on the quantum scattering coefficients. The combination of these methods allows calculating the electronic bands in the three directions mentioned above. We report the results of ordered slabs for Ag, described as s-like orbital and Ni given as d-type orbitals. To show the impact of expanding the crystal wavefunction, we reveal the calculation of the localized states for Rh, Cu, Pt given as d-type orbitals as first calculation then d9.5s1.5-coupling orbitals as second calculation. The results of the nonordered slabs are applied to Pd and Ir. Cutting the crystals affects the internal energy of the surface atoms, which will be subject to a relaxation effect until equilibrium is achieved
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    Electronic quantum scattering across molecular junctions: Oligoacenes and oligophenyl graphene strips
    (Elsevier, 2020) Belayadi, Adel; Bourahla, Boualem
    The use of molecular junctions has shown a constant development in the miniaturization of electronic devices. Because, understanding electron transport plays a key factor to develop potential applications in nanoelectronic. Additionally, in most recent studies, the Green functions were used as a powerful formalism to study electronic transport across atomic junctions. In this contribution, we involve an alternative model, based on the phase-field matching theory (PFMT) to investigate the electronic transport properties cross-molecular junctions. We focus on electric characterization and quantum scattering properties of Oligophenyl and Oligoacenes, both are examples of 1D-graphene nanoribbons. We show the impact of the PFMT by using a simple model system of two groups of semi-infinite monatomic chains of Gold (Au) or Silicon (Si), sandwiched together by molecular nanocontacts (Oligophenyl or Oligoacenes). The coherent transmission/reflection coefficients are calculated based on Landauer-Büttiker scattering matrix. The mathematical background of the PFMT is illustrated, we will consider the transport properties by using the Gold electrode instead of semi-infinite monatomic chains. In particular, we will investigate the effect of embedded atoms and magnetic fields across the molecular junction. The results exhibit an oscillation behavior of the transport properties under the presence of a magnetic field at the junction area
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