Partial substitution induced centrosymmetric to noncentrosymmetric structure transformation and promising second-order nonlinear optical properties of (K0.38Ba0.81)Ga2Se4

Partial substitution of Ba by K in the Ba sites of BaGa2Se4 creates a new selenide (K0.38Ba0.81)Ga2Se4 (1), which is crystallized in the noncentrosymmetric space group I4cm, different from the centric structures of all the ternary M-I-M-2(III)-Q(4) (M-II = divalent Sr, Ba, Pb, Sn, Eu; M-III = trivalent Ga, In; Q = S and Se) chalcogenides. Its 1D structure features {[GaSe2](-)}(infinity) chains, and K/Ba occupying the interchain cavities as the counter cations. Its powder sample demonstrates a second-harmonic generation intensity which is around 0.9 times that of AgGaS2 at 2.1 mu m, and a laser-induced damage threshold which is 13.4 times that of AgGaS2. DFT calculations on its electronic structure and optical properties were also performed.