High-Pressure Structural, Mechanical, Vibrational, and Electronic Study of Orthorhombic CaIn₂O₄

In this study, we use density functional theory (DFT) to explore the effects of pressure up to 31 GPa on the structural, mechanical, vibrational, and electronic properties of CaIn2O4 . Key properties such as hardness, rigidity, softness, elastic anisotropy, average sound velocity, Debye temperature, melting temperature, band gap, and vibrational frequencies (Raman and infrared) are analyzed at ambient pressure and tracked under increasing pressure. Our findings reveal that CaIn2O4 maintains both mechanical and dynamical stability up to 31 GPa, with no phase transitions observed within this pressure range. Increasing pressure leads to enhanced rigidity and elastic anisotropy. Moreover, the electronic structure analysis reveals that the band gap increases with pressure due to the upward shift of the In and O states. Vibrational frequencies, including Raman-active, infrared-active, and silent modes, increase with pressure, attributed to reduced bond lengths and strengthened force constants. These results highlight CaIn2O4 as a promising material for high pressure applications.