AgMAsS₃ (M = Cd, Hg): Double d¹⁰ Cation-Containing Thioarsenites(III) Exhibiting High Photocurrent Response and Moderate Second Harmonic Generation

Abstract

Thioarsenites(III) are an advanced functional material platform owing to the stereochemically active lone pair cations. In this paper, two novel quaternary thioarsenites(III), AgMAsS 3 (M = Cd, Hg), are successfully obtained by introducing double d 10 cations. In the compounds, d 10 cations show a variety of different coordination modes ([AgS 4 ] and [HgS 4 ] in AgHgAsS 3 vs [AgS 5 ] and [CdS 6 ] in AgCdAsS 3 ). As a result, AgHgAsS 3 and AgCdAsS 3 crystallize in the noncentrosymmetric Cc space group and centrosymmetric C2/c space group, respectively. The band gaps of AgHgAsS 3 and AgCdAsS 3 are determined experimentally as 1.90 and 2.20 eV, respectively. Meanwhile, title compounds exhibit strong photocurrent responses. Specifically, AgHgAsS 3 has a large birefringence of 0.18 at 2100 nm and a moderate second harmonic generation of (0.5 × AgGaS 2 ). Moreover, the origin of linear and nonlinear optical responses is investigated based on first-principles calculations. This study enriches the family of M I −M II −As− Q (M = Ag, Cu; M II = Zn, Cd, Hg; Q = chalcogen) chalcogenides and helps to understand and design other multifunctional optical materials.