MgSiAs: An Unexplored System with Promising Nonlinear Optical Properties

Abstract Two new non‐centrosymmetric ternary compounds, MgSiAs 2 and Mg 3 Si 6 As 8 , are discovered via metal flux and solid‐state synthetic methods. MgSiAs 2 belongs to the well‐known II‐IV‐V 2 family, which is extensively studied experimentally and computationally for their optical properties. MgSiAs 2 is computationally predicted but not experimentally known prior to this work. Mg 3 Si 6 As 8 crystallizes in a new non‐centrosymmetric cubic chiral structure type with the Pearson symbol cP 68. The syntheses, crystal structure, thermal and chemical stabilities, electronic structures, and optical properties of these two new compounds are investigated in this work. Optical absorption measurements and electronic structure calculations reveal the two compounds to be direct or pseudo‐direct bandgap semiconductors (1.8–2 eV). The crystal structures of both compounds are non‐centrosymmetric, though Mg 3 Si 6 As 8 belongs to the 432 chiral crystal class, which is optically active but does not exhibit second harmonic generation (SHG) behavior. The SHG response of MgSiAs 2 is 60% of that for AgGaS 2 , but MgSiAs 2 exhibits a higher laser damage threshold than AgGaS 2 at 33.2 MW cm −2 .