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<p>In this study, we investigated how pressure affects the structural, elastic, electrical, thermodynamic, and optical properties of the BaMg<sub>2</sub>Ge<sub>2</sub> and BaMg<sub>2</sub>Si<sub>2</sub> materials using two complementary ab initio computational methods implemented in the CASTEP and WIEN2k codes. The GGA-PBEsol functional was applied to model exchange–correlation interactions. The calculated equilibrium structural parameters and the counterpart experimental values are almost identical. Under compression, the lattice parameter <i>a</i> decreases more notably than the lattice parameter <i>c</i> in both compounds. The calculated single-crystal elastic constants and related phenomena show that both compounds meet the criteria for mechanical stability at pressures from 0 to 18&#xa0;GPa, with significant elastic anisotropy and a brittle character. Furthermore, the study considers polycrystalline elastic constants—including the bulk modulus (B), shear modulus (G), Young’s modulus (E), Poisson’s ratio, and related properties—up to 18&#xa0;GPa. Using the Debye quasi-harmonic model, the temperature- and pressure-dependent behavior of various macroscopic physical phenomena was assessed. Electronic structure calculations reveal that BaMg<sub>2</sub>Ge<sub>2</sub> and BaMg<sub>2</sub>Si<sub>2</sub> are conductors. The spectra of the real and imaginary parts of the dielectric function, the absorption coefficient, the optical conductivity, the loss-energy function, the reflectivity, the refractive index, and the extinction coefficient were determined for two polarization directions of incident radiation.</p>

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A first-principles study of pressure-induced modulations in structural, elastic, thermodynamic, electronic, and optical properties of BaMg2X2 (X = Ge, Si)

  • 期刊论文

  • 发表日期：

    2026年5月9日

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  • Amira Imessaoudene,
  • Missoum Radjai,
  • Abdelmadjid Bouhemadou,
  • Saber Saad Essaoud,
  • Said Maabed

摘要

In this study, we investigated how pressure affects the structural, elastic, electrical, thermodynamic, and optical properties of the BaMg2Ge2 and BaMg2Si2 materials using two complementary ab initio computational methods implemented in the CASTEP and WIEN2k codes. The GGA-PBEsol functional was applied to model exchange–correlation interactions. The calculated equilibrium structural parameters and the counterpart experimental values are almost identical. Under compression, the lattice parameter a decreases more notably than the lattice parameter c in both compounds. The calculated single-crystal elastic constants and related phenomena show that both compounds meet the criteria for mechanical stability at pressures from 0 to 18 GPa, with significant elastic anisotropy and a brittle character. Furthermore, the study considers polycrystalline elastic constants—including the bulk modulus (B), shear modulus (G), Young’s modulus (E), Poisson’s ratio, and related properties—up to 18 GPa. Using the Debye quasi-harmonic model, the temperature- and pressure-dependent behavior of various macroscopic physical phenomena was assessed. Electronic structure calculations reveal that BaMg2Ge2 and BaMg2Si2 are conductors. The spectra of the real and imaginary parts of the dielectric function, the absorption coefficient, the optical conductivity, the loss-energy function, the reflectivity, the refractive index, and the extinction coefficient were determined for two polarization directions of incident radiation.