Ab initio investigation of the elastic and piezoelectric properties of lithium based Chalcogenides LiMX2 (M = Ga,In; X = S,Se)

In this paper we report theoretical ab initio study of the elastic and piezoelectric properties of LiMX2 (M = Ga,In; X = S, Se) by means of density functional theory (DFT). Other relevant quantities such as shear modulus, Young’s modulus, sound velocity, Poisson’s ratio, anisotropy factors, and Debye temperature have been calculated. The calculated Debye temperatures for LiInS2 and LiInSe2 are very close to experimental counterparts. Moreover, we present for the first time the investigation of the piezoelectric properties of LiGaS2, LiGaSe2 and LiInSe2 using the density-functional perturbation theory (DFPT). The calculated piezoelectric tensors for LiInS2 are in good agreement with the experimental data. These compounds that have reached crystal growth maturity show good piezoelectric property. For example, the calculated d15 and d33 piezoelectric coefficients of LiGaSe2 are 5.02pN/C and 3.17pN/C respectively.

► LiGaS2(Se) and LiInSe2 are promising candidate for piezoelectric applications.
► The Gallium containing materials are stiffer than Indium counterpart.
► LiInS2 has the highest piezoelectric coefficients in these four compounds.
► These compounds present low C44 and C66 coefficient compared to quartz.