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

Thioarsenites(III) are an advanced functional material platform owing to the stereochemically active lone pair cations. In this paper, two novel quaternary thioarsenites(III), AgMAsS₃ (M = Cd, Hg), are successfully obtained by introducing double d¹⁰ cations. In the compounds, d¹⁰ cations show a variety of different coordination modes ([AgS₄] and [HgS₄] in AgHgAsS₃ vs [AgS₅] and [CdS₆] in AgCdAsS₃). As a result, AgHgAsS₃ and AgCdAsS₃ crystallize in the noncentrosymmetric Cc space group and centrosymmetric C2/c space group, respectively. The band gaps of AgHgAsS₃ and AgCdAsS₃ are determined experimentally as 1.90 and 2.20 eV, respectively. Meanwhile, title compounds exhibit strong photocurrent responses. Specifically, AgHgAsS₃ has a large birefringence of 0.18 at 2100 nm and a moderate second harmonic generation of (0.5 × AgGaS₂). 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.