Elastic properties of amorphous TiNiSn

The elastic properties of amorphous TiNiSn, a promising half-Heusler system for flexible and wearable devices, were investigated using experimental and theoretical methods. Nanoindentation measurements performed on amorphous TiNiSn thin film grown by magnetron sputtering yielded an elastic (Young's) modulus value of 132 GPa. To corroborate this result, density functional theory (DFT) calculations and two machine learning models were employed, where the latter were trained on available literature data. The DFT-derived elastic modulus of amorphous TiNiSn is 113 GPa (stress-free conditions), which is 15% lower than the experimental value. However, when hydrostatic stress is considered, arising from possible thermal loads and ion bombardment during thin film synthesis, the difference is reduced to 5%. Electronic structure analysis reveals that amorphous TiNiSn exhibits predominantly covalent bonding with a minor metallic contribution, which is consistent with the measured elastic modulus. Although both machine learning models underestimate the experimental modulus more than DFT, the theoretical results enhance understanding of the elastic behaviour of amorphous TiNiSn and highlight its potential for future applications in flexible microelectronic systems.