Theoretical investigations of substitution site and local structure distortion for tetragonal Cr2+ ion in AgGaSe2:Cr2+ compound

In this paper, the substitution site and local structure distortions for Cr2+ ion doped into AgGaSe2 crystal are studied by diagonalizing the full energy matrix within a strong-field basis. Our calculations show that the local structure has an expansion distortion when Ga3+ is substituted by Cr2+ ion, while has an expansion distortion along bond-length direction and a compression distortion along angular direction when Ag+ is substituted by Cr2+ ion. From ZFS parameter calculations, the local lattice structure parameters R = 2.59 Å and θ = 56.16° for Cr2+ occupying Ga3+ site, and R = 2.85 Å and θ = 55.97° for it occupying Ag+ site are determined.