title: BaGa4Se7: a new congruent-melting IR nonlinear optical material.
abstract: The new compound BaGa(4)Se(7) has been synthesized for the first time. It crystallizes in the monoclinic space group Pc with a = 7.6252 (15) Å, b = 6.5114 (13) Å, c = 14.702 (4) Å, β = 121.24 (2)°, and Z = 2. In the structure, GaSe(4) tetrahedra share corners to form a three-dimensional framework with cavities occupied by Ba(2+) cations. The material is a wide-band gap semiconductor with the visible and IR optical absorption edges being 0.47 and 18.0 μm, respectively. BaGa(4)Se(7) melts congruently at 968 °C and exhibits a second harmonic generation response at 1 μm that is approximately 2-3 times that of the benchmark material AgGaS(2). A first-principles calculation of the electronic structure, linear and nonlinear optical properties of BaGa(4)Se(7) was performed. The calculated birefractive indexΔn = 0.08 at 1 μm and the major SHG tensor elements are: d(11) = 18.2 pm/V and d(13) = -20.6 pm/V. This new material is a very promising NLO crystal for practical application in the IR region.
authors.affiliation: Center for Crystal Research and Development, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China.
authors.forename: Jiyong
authors.initials: J
authors.lastname: Yao
authors.forename: Dajiang
authors.initials: D
authors.lastname: Mei
authors.forename: Lei
authors.initials: L
authors.lastname: Bai
authors.forename: Zheshuai
authors.initials: Z
authors.lastname: Lin
authors.forename: Wenlong
authors.initials: W
authors.lastname: Yin
authors.forename: Peizhen
authors.initials: P
authors.lastname: Fu
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Wu