LiBa₂M^IIIQ₄ (M^III = Al, Ga, In; Q = S, Se): A Series of Metal Chalcogenides with a Structural Transition

Abstract

A series of metal chalcogenides, LiBa2MIIIQ4 (MIII = Al, Ga, In; Q = S, Se), have been successfully obtained by the sealed-tube method. LiBa2MIIIQ4 undergoes a special structural transformation from the P21/m (LiBa2AlQ4 and LiBa2GaS4) to the P21/n (LiBa2InQ4) space group, which leads to disparities in electronic states, birefringence, and band gaps. Their structures feature the same zigzag [LiMIIIQ4]4– layers consisting of corner-shared LiQ4 and MIIIQ4 tetrahedra. The Ba atoms serve to bridge the [LiMIIIQ4]4– layers. The structural comparisons show that the radii of MIII and the coordination environments of the Ba atoms (BaQ7 vs BaQ8) cooperatively affect the structural transition from simple mirror m to diagonal glide n in LiBa2MIIIQ4. In addition, a statistical analysis uncovers that the MIII/Ba atomic ratio also plays an important role in regulating the structural transition in Ba- and MIII-based chalcogenides.

Vast Structural and Polymorphic Varieties of Semiconductors AMM′Q4 (A = K, Rb, Cs, Tl; M = Ga, In; M′ = Ge, Sn; Q = S, Se)

“…The band structures and density of states (DOS) for these compounds can be found in the Supporting Information (Figures S11–S22). These calculations, our previously reported calculations for the gallium compounds, and other DFT calculations performed on these compounds ,,,,,, are very consistent and revealed that all of the quaternary AMM′Q 4 phases are semiconductors. Differences between the experimental and calculated band-gap values may result from a different M/M′ disorder used for the calculations compared to those of the real compounds.…”

“…For the alkali metal compounds, only marginal differences in the reported band-gap values are observed for a given structure type and element combination. Substitution of the alkali metal A + does not significantly influence the band-gap values, which is consistent with the fact that the alkali metal states do not contribute to the states close to the Fermi level in these and related compounds. ,,,,,, However, a red shift of the band gaps for the thallium sulfide compounds, compared to that for their alkali metal counterparts, can be observed, which likely results from the contributions of the electronic states of the Tl + lone pair and empty p-states leading to a shrinking of the band gaps.…”

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

“…The peaks at 398 and 306 cm –1 can be attributed to the characteristic vibrations of the Ga–S bonds, while the peak at 154 cm –1 is for the Ga–Se bonds in the GaQ 4 tetrahedral units. The weaker active peaks near 168 and 100 cm –1 should be related to the vibrations of Li/Ba–S and Li/Ba–Se, respectively. − …”

Synthesis and Characterizations of Two Tellurides β-BaGa2Te4 and Ba5Ga2Ge3Te12 with Flexible Chain Structure

“…Apart from MQ 4 units, a few compounds also contain ethane-like [Ge 2 Te 6 6– ] units with homonuclear Ge–Ge bonds, for example, Ba 2 Ge 2 Te 5 . Nevertheless, exploring novel materials with controllable tetrahedral frameworks is still a huge challenge …”

“…49 Nevertheless, exploring novel materials with controllable tetrahedral frameworks is still a huge challenge. 50 Optical Properties. The IR and Raman spectra are shown in Figure 6.…”