Li₄HgSn₂Se₇: The First Second-Order Nonlinear Optical-Active Selenide in the I₄–II–IV₂–VI₇ Diamond-like Family

Abstract

A new infrared nonlinear optical material with diamond-like structures, Li4HgSn2Se7, was synthesized by the traditional high-temperature solid-state method. It crystallizes in the non-centrosymmetric group Cc with all the LiSe4, HgSe4, and SnSe4 tetrahedra aligned in an additive manner. This material exhibits large second harmonic generation (SHG) about 3.6 times that of the benchmark AgGaS2 with phase-matching behavior. Detailed structural analysis and calculations reveal that (HgSe4) and (SnSe4) tetrahedra are main contributors for its strong nonlinearity. Moreover, the electronic states and distinct contribution to SHG of different Se species are also elucidated.

Li4MgGe2S7: The First Alkali and Alkaline‐Earth Diamond‐Like Infrared Nonlinear Optical Material with Exceptional Large Band Gap

“…Such a value is suitable for application in molecular sieves, and, for example, the small molecules and ions including N 2 (3.64 Å), H 2 (2.89 Å), and O 2 (3.46 Å) can pass through freely within the tunnel. The similar phenomena were also observed in other DL structures, such as CdSe (≈6 Å), [22] Li 2 MnSnSe 4 (≈5 Å) and Li 4 HgSn 2 Se 7 (≈5 Å) [23] . Moreover, the unique (Ge 2 S 7 ) 6− dimers are discovered in Li 4 MgGe 2 S 7 (Figure 2 d).…”

“…The similar phenomena were also observed in other DL structures,s uch as CdSe ( % 6 ), [22] Li 2 MnSnSe 4 ( % 5 )a nd Li 4 HgSn 2 Se 7 ( % 5 ). [23] Moreover,t he unique (Ge 2 S 7 ) 6À dimers are discovered in Li 4 MgGe 2 S 7 (Figure 2d). Owing to the presence of (Ge 2 S 7 ) 6À dimers,L i 4 MgGe 2 S 7 does not completely follow Pauling second rule,a nd the sulfur anions are not completely compensated in terms of local charge [13d] that results in the subtle distortion in the tetrahedra (Table S7).…”

Structural modification from centrosymmetric Rb4Hg2Ge2S8 to noncentrosymmetric (Na3Rb)Hg2Ge2S8: mixed alkali metals strategy for infrared nonlinear optical material design

“…The atomic-level theoretical calculations for (Na 3 Rb)Hg 2 Ge 2 S 8 crystal were performed by density functional theory 46 via the Material Studio package, which has been applied to many metal chalcogenides successfully. 47–49 In all calculations, 900 eV cutoff energy and (2 × 4 × 1) Monkhorst–Pack k -point meshes 50 were selected to ensure sufficient accuracy of the simulated results. The structural lattices and atomic positions were fixed the same as for single-crystal XRD refinement.…”

HgCuPS4: An Exceptional Infrared Nonlinear Optical Material with Defect Diamond-like Structure

“…In recent years, Hg-containing NCS metal chalcogenides have drawn wide attention in the IR-NLO field. − One the one hand, the Hg 2+ cation has various coordination environments to form three types of ABMs, i.e., linear [HgQ 2 ], trigonal-planar [HgQ 3 ], and tetrahedral [HgQ 4 ], which are the typical NLO-active motifs. On the other hand, the electron cloud of the Hg 2+ cation possesses much stronger deformability and polarizability compared to congener Zn 2+ and Cd 2+ cations, which would significantly boost the d ij and Δ n values.…”