Three new chalcohalides, Ba4Ge2PbS8Br2, Ba4Ge2PbSe8Br2 and Ba4Ge2SnS8Br2: Syntheses, crystal structures, band gaps, and electronic structures

Pb3SBrI3: the first Pb-based chalcohalide with multiple halogens features a unique two-dimensional structure composed of diverse Pb-centered polyhedra

“…4b). This value is comparable with ZnHg 3 Se 2 Cl 4 (2.23 eV), 59 Ba 4 Ge 2 SnS 8 Br 2 (2.07 eV), 45…”

“…4b). This value is comparable with ZnHg 3 Se 2 Cl 4 (2.23 eV), 59 Ba 4 Ge 2 SnS 8 Br 2 (2.07 eV), 45 and Ba 3 AGa 5 Se 10 Cl 2 (A = Cs, Rb, K) (2.08, 2.05, 2.04 eV), 60 but larger than some chalcohalides, such as Pb 2 BiS 2 I 3 (1.60 eV), 61 KBa 2 SnS 4 Br (1.95 eV), 62 CdSb 2 Se 3 Br (1.40 eV), 63 and InSb 2 S 4 Cl (1.80 eV). 63…”

“…The Pb–I bond lengths of the PbBr 2 I 4 octahedron are in the range of 3.211(2)–3.302(2) Å, and the distance of the Pb–Br bond is 3.078(16) Å. The bond distance of Pb–S (2.668(5)–2.799(3) Å) is shorter than those of the Ba 4 Ge 2 PbS 8 Br 2 (2.932(4)–3.044(4) Å) 45 and K 2 PbGe 2 S 6 (2.844(1)–3.150(2) Å), 46 but the distance of the Pb–I bonds (3.158(13)–3.372(13) Å) and the Pb–Br bond (3.078(16) Å) are comparable to those of Rb 3 Pb 2 (CH 3 COO) 2 Br 5 (3.1181(12)–3.2794(6) Å) 47 and Hg 2 PbI 2 S 2 (3.427(1)–3.433(1) Å). 48 Afterwards, one distorted PbBr 2 I 4 octahedron joins to four contiguous octahedra by edge-sharing and generates a [PbBrI 2 ] ∞ layer (layer B) that grows along the ab plane (Fig.…”