Theoretical Design of Layered AlGaS3 as a New Nonlinear Optical Material with a Strong Second Harmonic Generation Response Published as part of a Crystal Growth and Design virtual special issue on Crystalline Functional Materials in Honor of Professor Xin-Tao Wu

摘要

Using an evolutionary algorithm combined with first-principles calculations, the stoichiometry and the structure of a new family of Al-Ga-S ternary sulfides are explored, and a layered configuration with the R3m space group is predicted as the most stable structure of AIGaS(3). The second order nonlinear optical (NLO) properties of the AIGaS(3)-R3m phase are further calculated, and our results reveal that it is a promising candidate for mid-infrared NLO material. Besides the high laser damage threshold and the good phase match ability in the transmission range 0.4-24 ktm that covers most of the mid-IR windows, the second harmonic generation (SHG) of AIGaS(3)-R3m is about four times stronger than that of the commercial AgGaS2 crystal. The strong SHG activity of the AlGaS3-R3m phase can be attributed to a special layered arrangement of the structure, namely, two kinds of coordination polyhedra (i.e., [AlS6]9- octahedra and [GaS4](5-) tetrahedra) are distributed in the opposite sides of the single AIGaS(3) layer, which helps to strengthen the polarity of the material. Additionally, with respect to the layered structures, other phases of AIGaS(3) crystallized in condensed bulk structures that only contain tetrahedral motifs ([AlS4](5-) and [GaS4](5-)) show relatively weak SHG responses. The present study suggests that construction of a two-dimensional layered structure can provide an effective way to find new NLO materials with a strong SHG effect.