For the couple of chalcopyrite compounds, we have theoretically studied the various properties for example structural, electronic optical and mechanical properties. The band structure curve, the density of states as well as the total energy have been investigated with the help of ATK-DFT by using the pseudo-potential plane wave method. For the LiInS2 and LiInSe2 chalcopyrites, we have found that these compounds possess direct band gap; which is 3.85 eV and 2.61 eV for LiInS2 and LiInSe2

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... vely. It shows that the band gap is decreasing from 'S' to 'Se' as well as the B/G ratio called Pugh's ratio is 2.10 for LiInS2 and 2.61 for LiInSe2 so these compounds are ductile in nature also these compounds are found to be mechanically stable. The study of this work display that the couple of these chalcopyrite compounds can be the promising candidate for the substitution of absorbing layer in the photovoltaic devices.