Mechanical and dynamical stability, electronic and bonding properties of a new narrow-gap semiconductor YPdAs Half-Heusler: DFT and QTAIM study

YPdAs is a semiconductor with an indirect band-gap of a value close to that of the direct one. Despite its important semiconductor behaviour, this half-Heusler compound has not yet been synthesized. Therefore, the main objective of this work is to confirm its energetic, mechanical and dynamical stability to prove that it can be formed experimentally and exploit it in optoelectronic applications. We have adopted two calculation methods to ensure accuracy of the results: FP-LAPW and PPs. Both methods gave negative formation energy values, which confirmed the energetic stability of YPdAs. Furthermore, YPdHCAs structure is the most stable. In this structure, the estimated elastic stiffness constants Cij perfectly satisfy the mechanical stability criteria. The analysis of phonon dispersion curve has shown a similarity between the two adopted methods (Direct method and DFPT). Given the absence of soft modes, the dynamical stability is confirmed for the first time. From the above, we confirm the possibility of synthesizing this compound experimentally. The electronic results show that the band-gap is indirect. There is no band inversion between VBM and CBM, which shows the trivial nature of this semiconductor. The detailed analysis of the bonds between the different atoms of this compound using QTAIM has shown the presence of only two bonds (Y–Pd and Pd–As) that have a similar character of a dative nature.