Structural Chemistry and Excellent Nonlinear Optical Properties of a Series of Ternary Selenides Ga_<i>x</i>In_2–<i>x</i>Se₃

Abstract

Novel nonlinear optical (NLO) materials possessing simple chemical compositions and facile syntheses are competitive when considering their practical application. Here, a series of ternary selenides GaxIn2–xSe3 (x = 0.07, 0.38, 0.45, and 0.81) that crystallize in a chiral P65 structure are obtained by melting Ga, In, and Se elements. Their three-dimensional structures are built by (Ga/In)­Se4 tetrahedra and InSe5 trigonal bipyramids. The hexagonal modification’s phase stability is analyzed by energy calculation, and their optical band gaps are determined to be 1.72–1.99 eV. They exhibit large NLO responses that are 1.41–1.64 times that of the benchmark AgGaS2. The results of density functional theory calculations suggest that introduction of Ga onto the In site in (InSe4)5– units can form a deformed tetrahedron with more distortion in the structure, and the (InSe5)7– units contribute a large amount of birefringence to the structure. This work is the first to investigate the ternary chalcogenides M2Q3 (M = Ga or In; Q = S or Se) as new types of infrared NLO crystals with excellent performances, which will stimulate more interest in those possessing simple compositions and outstanding performances