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Found 7 items.

  • Effect of the paramagnetic to spin-glass phase transition on the fundamental absorption edge of MnIn2Se4 magnetic semiconducting compound

    Carlos Gustavo Rincón
    14-19
    2018-12-31
    Abstract:

        The temperature dependence of the indirect and direct fundamental band gaps of the layered compound MnIn2Se4,that crystallizes in a rhombohedral defect structure with space group R -3m (D5/3d), was studied by optical absorption spectra. The data were analyzedin terms of current theoretical models that take into account the contribution of antiferromagnetic exchange interaction between spins to the shift of the energy gap EG with T in the vicinity of the critical paramagnetic to spin-glass phase transition. It was established that short- and long-range effect spin correlations dominate the contribution to this shift in the critical region below about 20 K, near the spin-glass freezing temperature Tf, and noncritical one, between about 70 and 160 K, far from Tf, respectively. An intermediate temperature region, compatible with the behaviour expected for a cluster-glass transition where a gradual freezing of the magnetic moments occurs, was also observed.

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    DOI: https://doi.org/10.31349/RevMexFis.65.14

  • Impact of A-site cation substitution on the properties of pinel AY₂O₄ (A = Cd, Zn): A first-principles investigation

    K. Hocine, Y. Guermit, A. Chaabane
    051002 1–14
    2025-09-01
    Abstract:

    This study presents a comprehensive first-principles investigation of the structural, electronic, magnetic, elastic, thermodynamic, and optical properties of spinel-type compounds CdY₂O₄ and ZnY₂O₄ using density functional theory (DFT) within the full-potential linearized augmented plane wave (FP-LAPW) method. Structural optimization, performed through Murnaghan equation of state fitting and internal atomic relaxation, reveals that both compounds favor a nonmagnetic normal spinel configuration as their ground state. Electronic band structure calculations using PBE-GGA and TB-mBJ functionals demonstrate that both ZnY₂O₄ and CdY₂O4 are direct band gap semiconductors, with wide band gaps ranging from 4.86 to 4.93 eV. Elastic constants confirm mechanical stability, with CdY₂O₄ exhibiting ductile behavior and ZnY₂O₄ displaying higher stiffness but slightly brittle characteristics. Thermodynamic properties, evaluated via the quasi-harmonic Debye model, indicate that both materials maintain structural integrity up to 1200 K and 20 GPa, with ZnY₂O₄ showing superior thermal stability. Optical analyses reveal strong ultraviolet absorption, high transparency in the visible range, and low reflectivity, positioning these materials as promising candidates for UV optoelectronic applications, including UV filters, transparent conductive coatings, and window layers in tandem solar cells. The results highlight that cation substitution at the A-site (Cd²⁺ versus Zn²⁺) significantly influences the mechanical, thermal, and optical properties, making CdY₂O₄ and ZnY₂O₄ attractive for next-generation photovoltaic and photonic devices.

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    DOI: https://doi.org/10.31349/RevMexFis.71.051002

  • Assessing the viability of Caesium-based double perovskite for technological applications

    H. Mansour, D. Rached
    060503 1–9
    2025-11-01
    Abstract:

    This research aims to provide a comprehensive understanding of the structural, elastic, electronic, and optical properties of the Cs2PbBeBr6 halide double perovskite (HDP). In this study, all self-consistent field (SCF) calculations were performed using density functional theory (DFT) within the full-potential linear augmented plane-wave (FP-LAPW) method, as implemented in the Wien2k code. The Perdew-BurkeErnzerhof (PBE) generalized gradient approximation (GGA) and the Tran-Blaha modified Becke−Johnson (TB-mBJ) methods were employed to accurately describe the exchange-correlation interactions. Our findings indicate that Cs2PbBeBr6 is stable in a cubic structure (Fm-3m), supported by phase stability analysis, enthalpy of formation, tolerance factor, and elastic constants. The compound exhibits ductile behavior, as assessed by Poisson’s and Pugh’s ratios. The electronic band structure reveals an indirect band gap of 2.243 eV and 3.248 eV, calculated using the GGA and TB-mBJ methods, respectively. Optical spectra calculations were performed in the energy range of 0 to 13 eV for each of the dielectric functions, extinction coefficient, electron energy loss, refractive index, optical conductivity, reflectivity, and absorption coefficient. The optical properties of Cs2PbBeBr6 in the visible range are particularly significant, offering strong potential for applications such as solar energy harvesting. These characteristics make the compound a promising candidate for optoelectronic devices.

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    DOI: https://doi.org/10.31349/RevMexFis.71.060503

  • Evolution of electronic bandgap by anion variation to explore niobium new halide double perovskites Cs2GeNbX6 (X = Cl, Br, I) for solar cells and thermoelectric applications: first principles analysis

    Abbes Labdelli, F.Bendahma, M.Mana, N.Benderdouche
    061001 1–12
    2023-11-01
    Abstract:

    The structural, electronic, optical, and thermoelectric properties of the niobium new halide double perovskites Cs2GeNbX6 (X = Cl, Br, I) were investigated using a density functional theory method. The generalized gradient approximation (GGA) method is used to project the exchange-correlation potential. The tolerance factor and optimizing total energy define the structure's stability. The magnetic moments of our compounds are high, more than 3μB. The compounds have direct narrow band gaps of 0.69, 0.46, and 0.26 eV, respectively, for Cs2GeNbCl6, Cs2GeNbBr6, and Cs2GeNbI6, as determined by band structure calculations. This is ideal for investigating these compounds for use in solar cells. In addition, the investigated compounds were investigated in terms of optical absorption, refractive index, and dielectric constants for energy range 0–12 eV, ensuring absorption in infrared, visible, and ultraviolet regions. This was done in order to study optical characteristics. The investigated compounds are excellent candidates for harvest solar cell applications due to their maximum visible absorption. They are also good candidates for thermoelectric applications due to their Seebeck coefficient, lattice thermal, electric conductivities and figure of merit (ZT) addressed by Boltzmann theory.

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    DOI: https://doi.org/10.31349/RevMexFis.69.061001

  • FrYBi (Y = Ca, Sr, Ba) Semiconductors for Visible-Light Harvesting: A multifunctional platform for energy conversion and optoelectronic applications

    O. Hammadache, M. Houari, S. Mesbah, K. Khelifa-Kerfa, M. Benghanem, T. Lantri, B. Belarbi
    1-10
    2026-07-01
    Abstract:

    This study presents a comprehensive first-principles investigation of the structural, electronic, optical, elastic, and thermoelectric properties of the novel half-Heusler compounds FrYBi (Y = Ca, Sr, Ba). Employing density functional theory (DFT) with both the GGA-PBE and mBJ-GGA approximations, we determine that these compounds crystallise in the cubic Clb structure and exhibit indirect band gaps ranging from 0.97 to 1.35 eV, confirming their semiconducting nature. Detailed optical analyses reveal high absorption coefficients, pronounced reflectivity, and favourable dielectric responses within the visible spectrum, indicating potential for optoelectronic applications. Calculations of the elastic properties demonstrate that all compounds are mechanically stable and exhibit ductile behaviour. Thermoelectric analysis indicates high Seebeck coefficients alongside good electrical conductivity, particularly at low to moderate temperatures, suggesting promising performance for energy conversion applications. These findings position FrYBi alloys as compelling candidates for next-generation thermoelectric and optoelectronic devices.

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    DOI: https://doi.org/10.31349/RevMexFis.72.040502

  • The fundamental absorption edge of CuGa3Te5 ordered defect semiconducting compound

    G. Marín, C. Rincón, S.M. Wasim, G. Sánchez-Pérez
    593-596
    2017-01-01
    Abstract:
    The analysis of the temperature variation of the optical absorption spectra of the ordered defect compound CuGa3Te5, a semiconducting material which crystallizes in a chalcopyrite-related structure with space group P¹4 2c, is made. It has been established that this compound has a direct-allowed band gap between parabolic bands which varies from 1.187 to 1.090 eV in the temperature range from 10 to 300 K. The mean temperature of the phonon involved in the direct band-to-band transition is µ ¼ 125 K. This is comparable with 3/4 µD ¼ 156 K, µD being the Debye temperature of the compound.
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    DOI: https://doi.org/10.31349/RevMexFis.63.6.593

  • DFT-based analysis of structural, electronic, optical, mechanical, and thermodynamic characteristics of Rb2YAuX6 (X = Br, Cl) double perovskites for energy conversion applications

    A. Merrad, H. Bouchenafa, B. Benichou
    1-13
    2026-07-01
    Abstract:

    We investigated the potential of the double perovskite halides Rb2YAuX6 (X = Br, Cl) for renewable energy applications using density functional theory (DFT) with the full-potential linearized augmented plane wave (FP-LAPW) method. These compounds are structurally stable in the cubic Fm-3m phase and demonstrate excellent mechanical strength. Electronic structure calculations revealed that the compounds are indirect band gap semiconductors, with energy gaps ranging from 1.58 to 2.01 eV when using the PBE-GGA approximation, and from 3.49 to 3.70 eV when using the TB-mBJ potential. Optical analysis shows strong ultraviolet (UV) absorption and low reflectivity in the visible range. We estimated the thermodynamic properties as a function of temperature using the quasi-harmonic Debye model. Key thermal parameters, including entropy, specific heat capacity, and the Debye temperature, were calculated to evaluate thermal stability at high temperatures. These results are crucial for evaluating the suitability of Rb2YAuX6 (X = Br, Cl) compounds for use in industrial and high-temperature environments. This work represents the first predictive theoretical investigation of these materials, as no prior experimental or computational studies have been conducted on them. Our findings suggest that these double perovskites could be ideal for next-generation photovoltaic and energy harvesting applications.

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    DOI: https://doi.org/10.31349/RevMexFis.72.040501
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