A DFT investigation of energetic, elastic and dynamical stability and optoelectronic properties of a novel LaPtSb narrow band-gap semiconductor

LaPtSb half-Heusler is a novel narrow band-gap semiconductor that has not yet been synthesized. The importance of this physical behaviour is the reason behind our study that shows for the first time that this compound is energetically, elastically and dynamically stable, which underlines the possibility of synthesizing it. All calculated formation energy values for the different possible structures of LaPtSb are negative, confirming its energetic stability. However, the most stable structure is that where Pt occupies the heterocubic site (LaPt HC Sb), which indicates that it is of the ground state . The calculated elastic stiffness constants C ij show that LaPt HC Sb is elastically stable, which confirms that this structure resists under the effect of slight mechanical stresses. Analysis of the directional surface of Young's modulus shows that LaPt HC Sb has a weak elastic anisotropy . The analysis of phonon dispersion curve shows the absence of imaginary frequency branches (soft modes), which shows, for the first time, that LaPt HC Sb is dynamically stable. These results show that LaPt HC Sb maintains its dynamical stability even at very low temperatures (ground state). These stabilities confirm that LaPt HC Sb can be formed experimentally. The optoelectronic study with TB-mBJ+SOC showed that LaPt HC Sb is a narrow band-gap semiconductor (of 0.15 eV) of a direct nature of - type. This study shows that this compound has very important optoelectronic properties and can be used in several application fields.