Synthesis, structure, and electronic structure of CsAgGa2Se4

► New chalcogenide CsAgGa2Se4 has been synthesized. ► It possesses a new structure type with ∞2[AgGa2Se4]− layers separated by Cs+ cations. ► ∞2[AgGa2Se4]− consists of a ∞2[Ag2GaSe6]7− sublayer sandwiched by ∞1[Ga3Se8]7− chains. ► Band gap of CsAgGa2Se4 is mainly determined by the 4s, 4p orbitals of Ga and Se.