K2CdGe3S8: A New Infrared Nonlinear Optical Sulfide

A quaternary metal chalcogenide, namely K2CdGe3S8(I), is obtained through a high-temperature solid-state approach. CompoundIcrystallizes with the non-centrosymmetric space groupP212121. It features a 2D layer structure with [CdGe3S8] layers consisting of tetrahedral GeS4and CdS4units, and counter K+embedded between the layers. The compound exhibits a powder second-harmonic generation (SHG) response of ~0.1 times that of KH2PO4(KDP) with phase-matchable character at the laser wavelength of 1064 nm. Remarkably, it has a wide band gap (3.20 eV), which corresponds to a favorable high laser-induced damage threshold of 6.7 times that of AgGaS2. In addition, the calculated birefringence (Δn) is 0.039 at the wavelength of 1064 nm, which satisfies the Δncriteria for a promising infrared NLO material.