Defect Formation Energies in Chalcopyrite-Type AgInSe2 and the Rerated Chalcopyrite Compounds by First Principles Calculations

First-principles pseudopotential calculations using plane-wave basis functions were performed to quantitatively evaluate the formation energies of atomic vacancies in chalcopyrite-type AgInSe₂, and the related chalcopyrite compounds, AgGaSe₂ and AgAISe ₂. In all these chalcopyrite-type AgMSe₂ (M=In, Ga, Al), the formation energy of Ag vacancy is smaller than those of the other atomic vacancies. Formation energy of the Ag vacancy in AgInSe₂ is greatly dependent on the chemical potentials of constituent elements. The formation energy of Ag vacancy in AgMSe₂ (M=In, Ga, Al) is larger than that of Cu vacancy in CuMSe₂ . The result indicates that the Ag vacancy in AgMSe₂ is more difficult to be formed than the Cu vacancy in the corresponding Cu-based chalcopyrite compounds