First-Principles Investigation of Pressure-Induced Structural, Elastic, and Vibrational Properties of In3Sc

This study reports a first-principles investigation of the structural, mechanical, electronic, and vibrational properties of In3Sc in several crystal structures: AuCu3 (Pm3¯m), Al3Ti (I4/mmm), Ni3Sn (P63/mmc), and BiF3 (Fm3¯m), with a focus on pressure effects. Calculated equilibrium lattice constants, bulk, shear, and Young’s moduli show good agreement with experimental and theoretical data, especially for the cubic AuCu3 phase. Elastic constants, examined with the Born stability criteria, reveal that the cubic (SG 221), tetragonal (SG 139), and hexagonal (SG 194) phases are mechanically stable at zero pressure, while the BiF3-type cubic (SG 225) is unstable. Pressure-dependent variations in lattice parameters, bulk modulus, and elastic moduli, captured by polynomial fits, demonstrate stiffening effects and pressure-induced phase transitions. Band structures and density of states confirm metallicity in all stable phases, with In–Sc hybridization governing bonding. Phonon dispersions and Grüneisen parameters, calculated under compression, establish the dynamical stability of the mechanically stable structures and provide insight into vibrational and thermal behavior. Debye temperature and sound velocities highlight favorable thermal-transport features. Altogether, the results clarify the intrinsic mechanical and thermodynamic response of In3Sc, supporting its potential as a promising intermetallic for structural and functional use under extreme conditions.