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<p>In this study, a comprehensive first-principles investigation is performed on the quaternary (312) MAX phases Cr<sub>2</sub>ScSiC<sub>2</sub> and Cr<sub>2</sub>TiSiC<sub>2</sub> using density functional theory within the FP-LAPW framework. Structural optimization and formation energy calculations confirm the thermodynamic stability of both compounds, with Cr<sub>2</sub>TiSiC<sub>2</sub> exhibiting a stiffer lattice and a more exothermal formation energy (− 0.52&#xa0;eV/atom) compared to Cr<sub>2</sub>ScSiC<sub>2</sub> (− 0.41&#xa0;eV/atom). Substitution of Sc by Ti leads to a significant enhancement in lattice stiffness, manifested by higher elastic constants and superior bulk (B) and shear (G) moduli. As a result, Cr<sub>2</sub>TiSiC<sub>2</sub> demonstrates a higher Young’s modulus (~ 313 GPa) and Vickers hardness (~ 16.1 GPa), indicating superior resistance to elastic and plastic deformation. Electronic band structure and density-of-states (DOS) analyses reveal a clear metallic behaviour for both phases, primarily dominated by Cr-3d states near the Fermi level (E<sub>F</sub>). The Ti-containing phase exhibits stronger d–p orbital hybridization and a higher density of states at E<sub>F</sub>, suggesting enhanced electronic conductivity and a more stable electronic framework. Thermodynamic properties show that Cr<sub>2</sub>TiSiC<sub>2</sub> possesses a higher Debye temperature (~ 730&#xa0;K), reduced thermal expansion, and improved vibrational rigidity. These trends are attributed to the higher valence electron concentration (VEC) and optimized interatomic bonding introduced by Ti-incorporation. The present results suggest that Cr<sub>2</sub>TiSiC<sub>2</sub> exhibits a combination of mechanical robustness, thermal stability, and reduced heat transport, making it a promising system for further investigation in high-temperature environments.</p>

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First-principles investigation of structural, mechanical, electronic and thermodynamic properties of Cr2ScSiC2 and Cr2TiSiC2 MAX phases for advanced thermal barrier systems

  • 期刊论文

  • 发表日期：

    2026年6月17日

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  • Amine Abdelkader Guermoudi,
  • Ahmed Azzouz-Rached,
  • Yazen M. Alawaideh

摘要

In this study, a comprehensive first-principles investigation is performed on the quaternary (312) MAX phases Cr2ScSiC2 and Cr2TiSiC2 using density functional theory within the FP-LAPW framework. Structural optimization and formation energy calculations confirm the thermodynamic stability of both compounds, with Cr2TiSiC2 exhibiting a stiffer lattice and a more exothermal formation energy (− 0.52 eV/atom) compared to Cr2ScSiC2 (− 0.41 eV/atom). Substitution of Sc by Ti leads to a significant enhancement in lattice stiffness, manifested by higher elastic constants and superior bulk (B) and shear (G) moduli. As a result, Cr2TiSiC2 demonstrates a higher Young’s modulus (~ 313 GPa) and Vickers hardness (~ 16.1 GPa), indicating superior resistance to elastic and plastic deformation. Electronic band structure and density-of-states (DOS) analyses reveal a clear metallic behaviour for both phases, primarily dominated by Cr-3d states near the Fermi level (EF). The Ti-containing phase exhibits stronger d–p orbital hybridization and a higher density of states at EF, suggesting enhanced electronic conductivity and a more stable electronic framework. Thermodynamic properties show that Cr2TiSiC2 possesses a higher Debye temperature (~ 730 K), reduced thermal expansion, and improved vibrational rigidity. These trends are attributed to the higher valence electron concentration (VEC) and optimized interatomic bonding introduced by Ti-incorporation. The present results suggest that Cr2TiSiC2 exhibits a combination of mechanical robustness, thermal stability, and reduced heat transport, making it a promising system for further investigation in high-temperature environments.