In the present work, the structural, mechanical, electronic and optical properties of the Ruddlesden-Popper(RP) Ba 3 X 2 S 7 (X ¼ Zr, Hf, Ti) sulfides compounds have been investigated by means of first principles calculations. The generalized gradiend approximation has been used for modeling exchange-correlation effects. It has been observed that the calculated lattice parameters are in good agreement with the experimental values. Bulk modulus, shear modulus, Young's modulus Poisson's ratio, and Poisson's ratio from the calculated elastic constants for Ba 3 Zr 2 S 7 , Ba 3 Hf 2 S 7 , and Ba 3 Ti 2 S 7 compounds, respectively have been obtained. The obtained electronic band structure for Ba 3 Zr 2 S 7 and Ba 3 Hf 2 S 7 compounds are semiconductor in nature, and the Ba 3 Ti 2 S 7 compound also is metallic. Based on the obtained electronic structures, we further calculated the frequency-dependent dielectric function and other optical functions along the x-and z-axes.
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