Effect of Element Substitution on Structural Transformation and Optical Performances in I₂BaM^IVQ₄ (I = Li, Na, Cu, and Ag; M^IV = Si, Ge, and Sn; Q = S and Se)

Abstract

In the exploration of new infrared nonlinear optical (IR NLO) materials, element substitution has been developed as an effective way to adjust the structural features and material performances. A series of new IR NLO materials have been discovered in the I-Ba-M-Q system ( I = Li, Na, Cu, and Ag; M = Si, Ge, and Sn; Q = S and Se), and they undergo interesting structural transformation with different element substitution except Li analogues. Herein, we have successfully synthesized three selenides with different space groups (AgBaSiSe: I4̅2 m; AgBaGeSe and AgBaSnSe: I222) in the above system and studied their properties through experimental and theoretical methods. Remarkably, the detailed analysis on the structural changes and properties comparison was also systematically investigated in the I-Ba-M-Q system and the results indicate that the distortion degrees of different IQ tetrahedra play the critical role to cause the structural transformation with the M or Q elements substitution. More importantly, we have also found that the structural changes have the close relationship with the distance d( I- I) between adjacent I cations in the IBaSnSe system, which makes the four-membered rings formed by edge-sharing BaSe units change from the square to rhombus with the increase of d( I- I). The properties comparisons (band gap and NLO effect) in this system have been also systematically studied.

Unprecedented mid-infrared nonlinear optical materials achieved by crystal structure engineering, a case study of (KX)P2S6 (X = Sb, Bi, Ba)

“…The 3.220(5) Å K-S interactions are revealed by theory calculations as weak ionic bonds (vide infra). The Ba-S interactions in [BaS 10 ] polyhedra fall into the range of 3.226(3)-3.535(7) Å, which are close to many barium-sulfides such as Ba 6 (Cu 2 Mg)Ge 4 S 16 (3.084-3.454 Å), [53] Ba 2 P 2 S 6 (3.217-3.567 Å), [31] Ba 2 AlSbS 5 (3.217-3.567 Å), [54] BaAg 2 GeS 4 (3.251-3.306 Å), [55] BaCd 2 As 2 S 6 (3.248-3.374 Å), [56] etc. The 3.24 Å ionic Ba-S interactions exhibit certain bond strengths as revealed by theory calculations (vide infra).…”

Structural, Optical, and Electronic Properties of Two Quaternary Chalcogenide Semiconductors: Ag2SrSiS4 and Ag2SrGeS4

“…Here, we use past surveys of the I 2 –II–IV–X 4 family to predict the crystal structures of Ag 2 SrSiS 4 and Ag 2 SrGeS 4 and to further increase the accuracy of a previously developed tolerance factor approach, i.e., a pair of geometry-based descriptors designed to predict which different possible crystal structures form for particular members of the broader quaternary family. − We have synthesized powders and single crystals of these two semiconductors, finding that they are isostructural and form in the noncentrosymmetric tetragonal space group I 4̅2 m , like previously studied compounds Ag 2 BaGeS 4 , Ag 2 BaSiSe 4 , and Ag 2 BaSiS 4 . During the synthesis of these two new compounds, a secondary phase is often found to co-exist with Ag 2 SrSiS 4 and Ag 2 SrGeS 4 , unless the compounds are prepared under Sr-poor conditions.…”

Synthesis, crystal structure, and electronic structure of Li2PbSiS4: a quaternary thiosilicate with a compressed chalcopyrite-like structure

“…of optical bandgaps that span the entire visible spectrum and go into the ultraviolet. For example, the optical bandgap of Ag 2 BaSiSe 4 is in the red region of the visible spectrum, with E g = 1.83 eV (Nian et al, 2018), while that of Li 2 SrSiS 4 lies in the UV at 3.94 eV (Yang et al, 2020). In order to investigate the nature of the bandgap in the title compound, electronic structure calculations were employed.…”