(Cs6Cl)6Cs3[Ga53Se96]: A Unique Long Period-Stacking Structure of Layers Made from Ga2Se6 Dimers via Cis or Trans Intralayer Linking

The new compound (Cs6Cl)(6)Cs-3[Ga53Se96] with its own structure type has been discovered by high-temperature solid-state reactions. The compound features a unique long period-stacking structure of layers that are built by the commonly observed dimeric Ga2Se6 unit extending in cis or trans intralayer linking. Single-crystal X-ray diffraction analyses show the trigonal space group R (3) over barm (No. 166) and a = 11.990(5) angstrom, c = 50.012(4) angstrom, and V = 6226.5(6) angstrom 3. The UV-vis-near-IR spectrum reveals a wide band gap of 2.74 eV that agrees well with the electronic structure calculation.