LiBa₄Ga₅Q₁₂ (Q = S, Se): Noncentrosymmetric Metal Chalcogenides with a Cesium Chloride Topological Structure Displaying a Remarkable Laser Damage Threshold

Abstract

The exploration of novel infrared nonlinear optical (IR NLO) materials with large second-harmonic generation (SHG) responses and wide band gaps has become very imperative recently. Herein we reported two noncentrosymmetric compounds, LiBa4Ga5Q12 (Q = S, Se), crystallizing in space group P 21 c (No. 114), which feature 3D frameworks built by a basic [Ga5Q16]17– windmill cluster and LiQ4 tetrahedra in a cesium chloride topological structure. Both compounds satisfy the desired balance between good SHG responses (∼1.5× that of AgGaS2) and wide band gaps (3.43 and 2.44 eV) with remarkable laser damage thresholds (21× and 6× that of AgGaS2). The theoretical calculations uncover that the [Ga5Q16]17– cluster makes major contributions to the SHG effect in LiBa4Ga5Q12. In addition, the structure–performance relationship among all compounds in the I–II4–III5–VI12 system has been discussed systematically, which indicates that the introduction of the alkali metal lithium in the I site is beneficial for the production of large band gaps. This work will be helpful in exploring novel IR NLO materials with special structures and comprehensive properties in the chalcogenide system.

Syntheses, Structures and Properties of Alkali and Alkaline Earth Metal Diamond-Like Compounds Li2MgMSe4 (M = Ge, Sn)

“…To confirm chemical bonding, the Raman spectrum of Li 2 MgSnSe 4 was characterized on a single crystal. As shown in Figure 2 b, the peaks below 193 cm −1 are related to the vibrations of Li-Se and Mg-Se bonding, matched with the previous results [ 47 , 48 , 49 ]. The peak at 193 cm −1 and the overlapping peaks around 235 cm −1 could be assigned to the asymmetric and symmetric stretching vibrations of Sn-Se bonding in SnSe 4 tetrahedral groups [ 49 , 50 ].…”

Na4Ga8S14: a Ga-enriched wide band gap ternary alkali-metal sulfide with unique [Ga12S42] 12-membered rings

“…Interestingly, for the tunnel-like Ga-S 3D frameworks, the shape of the tunnels shows abundant diversity. Different from the 6-membered ring tunnel-like 3D framework in BaGa 4 S 7 , BaGa 4 Se 7 and LiGaS 2 , 20,24,25,55 and the 12-membered ring rectangular tunnel-like 3D framework in LiBa 4 Ga 5 Se 12 , 49 the formed 12-membered ring-like tunnels in Na 4 Ga 8 S 14 are rarely reported.…”

“…1a and S1, Table S3 †). 49 The Na atoms are connected with six S atoms to build [NaS 6 ] polyhedral groups with Na-S bond lengths of 2.740-3.531 Å (Fig. 1a and S1, Table S3 †).…”

“…3c, the peaks below 200 cm −1 can be attributed to the characteristic vibrations of Na-S bonding, while the peaks around 336, 374 and 394 cm −1 can be attributed to the characteristic vibrations of the Ga-S bond in the GaS 4 tetrahedral units. 49,[56][57][58] The UV-vis-NIR diffuse reflectance spectrum of the title compound was measured using the synthesized pure phase polycrystalline powder samples. To evaluate the experimental band gap of the title compound, the UV-vis-NIR diffuse reflectance spectrum was transformed to the absorption spectrum based on the Kubelka-Munk function.…”

Achieving a strong second harmonic generation response and a wide band gap in a Hg-based material

“…The assignments for the Raman peaks are consistent with those of other chalcogenides, such as LiBa 4 Ga 5 S 12 , (Na 3 Rb)Hg 2 Ge 2 S 8 and BaHgS 2 . [33][34][35] As [Ba 4 Cl 2 ][HgGa 4 S 10 ] crystallizes in the noncentrosymmetric space group of I4 ˉ, and contains the NLO-active [GaS 4 ] and [HgS 4 ] tetrahedra, a relatively large SHG response could be expected.…”