Hybrid perovskites have generated a great deal of interest because of their potential in photovoltaic applications. However, the toxicity of lead means that there is interest in finding a nontoxic substitute. Bulk single crystals of both cubic CH3NH3 SnI3 and CH(NH2)2 SnI3 were obtained by using the top-seeded solution growth method under an ambient atmosphere. Structural refinement, band gap, thermal properties, and XPS measurements of CH3NH3 SnI3 and CH(NH2)2 SnI3 single crystals are also reported in detail. These results should pave the way for further applications of CH3NH3 SnI3 and CH(NH2)2 SnI3.

Two new transition-metal-containing Zintl phases, Ca2CdSb2 and Yb2CdSb2, have been synthesized by flux reactions, and their structures have been determined by single-crystal X-ray diffraction. Yb2CdSb2 crystallizes in the noncentrosymmetric orthorhombic space group Cmc21 (No. 36, Z = 4). Ca2CdSb2 crystallizes in the centrosymmetric orthorhombic space group Pnma (No. 62, Z = 4). Despite the similarity in their chemical formulas and unit cell parameters, the structures of Yb2CdSb2 and Ca2CdSb2 are subtly different: Ca2CdSb2 has a layered structure built up of infinite layers of CdSb4 tetrahedra connected through corner-sharing. These layers are stacked in an alternating AA-1AA-1 sequence along the direction of the longest crystallographic axis (A denotes a layer; A-1 stands for its inversion symmetry equivalent), with Ca2+ cations filling the space between them. The structure of Yb2CdSb2 features the very same [CdSb2]4- layers of CdSb4 tetrahedra, which because of the lack of inversion symmetry are stacked in an AAAA-type fashion and are separated by Yb2+ cations. Electronic band structure calculations performed using the TB-LMTO-ASA method show a small band gap at the Fermi level for Ca2CdSb2, whereas the gap closes for Yb2CdSb2. These results suggest narrow gap semiconducting and poorly metallic behavior, respectively, and are confirmed by resistivity and magnetic susceptibility measurements. The structural relationship between these new layered structure types and some well-known structures with three-dimensional four-connected nets are discussed as well.

Seven cadmium- and zinc-containing Zintl phases, A9Zn(4+x)Pn9 and A9Cd(4+x)Pn9 (0 < or = x < or = 0.5), A = Ca, Sr, Yb, Eu; Pn = Sb, Bi, have been synthesized, and their structures have been determined by single-crystal X-ray diffraction. All compounds are isostructural and crystallize in the centrosymmetric orthorhombic space group Pbam (no. 55, Z = 2), and their structures feature tetrahedra of the pnicogens, centered by the transition metal. The tetrahedra are not isolated but are connected through corner sharing to form ribbons, which are separated by the divalent cations. The occurrence of a small phase width and its variation across this family of compounds has been systematically studied by variable temperature crystallography, resistivity, and magnetic susceptibility measurements, and these results have been reconciled with electronic structure calculations performed using the tight-binding linear muffin-tin orbital (TB-LMTO-ASA) method. These analyses of the crystal and electronic structure indicate that the polyanionic subnetwork requires 19 additional electrons, whereas only 18 electrons are provided by the cations. Such apparent "electron deficiency" necessitates the presence of an interstitial atom in order for an optimal bonding to be achieved; however, an interplay between the sizes of the cations and anions and the total valence electron concentration (governed by the stoichiometry breadth) is suggested as a possible mechanism for achieving structure stability. The structural relationship between these and some known structures with two-dimensional layers are discussed as well.

The hybrid perovskites with special optoelectronic properties have attracted more attention to the scientific and industrial applications. However, because of the toxicity and instability of lead complexes, there is interest in finding a nontoxic substitute for the lead in the halides perovskites and solving the ambiguous crystal structures and phase transition of NH(CH 3 ) 3 SnX 3 (X = Cl, Br). Here, we report the bulk crystal growths and different crystal morphologies of orthorhombic hybrid perovskites NH(CH 3 ) 3 SnX 3 (X = Cl, Br) in an ambient atmosphere by bottom-seeded solution growth (BSSG) method. More importantly, detailed structural determination and refinements, phase transition, band gap, band structure calculations, nonlinear optical (NLO) properties, XPS, thermal properties, and stability of NH(CH 3 ) 3 SnX 3 (X = Cl, Br) single crystals are demonstrated. NH(CH 3 ) 3 SnCl 3 single crystal undergoes reversible structural transformation from orthorhombic space group Cmc2 1 (no. 36) to monoclinic space group Cc (no. 9) and NH(CH 3 ) 3 SnBr 3 belongs to the orthorhombic space group Pna2 1 (no. 33) by DSC, single-crystal X-ray diffraction and temperature-dependent SHG measurements, which clarify the former results. These results should pave the way for further studies of these materials in optoelectronics.

A novel 2D material germanane (GeH), which was synthesized by an ion-exchange approach, was firstly found to exhibit photocatalytic performance in the hydrogen evolution of water splitting and decomposition of organic contaminants under illumination of visible light (λ ≥ 420 nm).

Reported are structure and property studies on a series of isostructural compounds with general formulas Yb 9 Mn 4þx Sb 9 (x ≈ 0.2), A 9 Mn 4þx Bi 9 (A = Ca and Yb; x ≈ 0), and the Zn-substituted derivatives Yb 9 (Mn,Zn) 4þx Sb 9 (0 < x < 0.4). They have been synthesized from the corresponding elements by high-temperature reactions, and their structures have been established by single-crystal X-ray diffraction. Despite being nearly stoichiometric phases, whose average crystallographic arrangement can be described with the orthorhombic Ca 9 Mn 4 Bi 9 type structure (space group Pbam, No. 55), these ternary materials exist within narrow homogeneity ranges, whereupon an interstitial site is partially occupied by the transition metal. Electronic structure calculations confirm that the "empty" A 9 Mn 4 Sb 9 or A 9 Mn 4 Bi 9 structures are electron deficient, making them suitable hosts for small dopant atoms. The expected poorly metallic behavior is evidenced from temperature-dependent resistivity data gathered from single-crystals. Magnetic susceptibility measurements in the range 2-350 K reveal complex antiferromagnetically coupled structures. These experimental results are further corroborated by theoretical calculations based on the linear muffin-tin orbital (LMTO) and the full potential linearized augmented plane wave (FP-LAPW) methods. †

Four new Zintl compounds, Ba21Cd4Sb18, Ba21Cd4Bi18, Sr21Cd4Bi18, and Eu21Cd4Bi18, have been synthesized and structurally characterized. Despite the similarity in their chemical formulas and regardless of their identical electronic requirements, the structures of the Ba compounds and the Sr and Eu compounds are subtly different. Due to the cations, a cleavage of a selected pnicogen-cadmium bond occurs and the structures adapt to a novel packing of the resultant heteronuclear anions.

Reported are the synthesis of the new ternary compound Ba3Cd2Sb4 and its structure determination by single-crystal X-ray diffraction. Ba3Cd2Sb4 crystallizes with the monoclinic space group C2/m (No. 12); unit cell parameters a = 17.835(2) A, b = 4.8675(5) A, c = 7.6837(7) A, and beta = 112.214(1) degrees; Z = 4. Its structure can be viewed as made of Ba2+ cations and [Cd2Sb4] double chains that are interconnected through Sb-Sb bonds to form 2D infinity2[Cd2Sb4]6- layers. The bonding arrangement in Ba3Cd2Sb4 can also be derived from other known structure types that feature similar fragments, such as TiNiSi, Ca3AlAs3, and Ca5Al2Sb6. Tight-binding linear muffin-tin-orbital band structure calculations are presented as well and show that the constituent elements have closed-shell configurations, indicative of Ba3Cd2Sb4 being a Zintl phase with poor metallic behavior. Crystal orbital Hamilton population analyses on selected atomic interactions in this structure are discussed within the context of the site preference, manifested in the mixed-cation compounds and Ba3-xAxCd2Sb4, where A = Ca, Sr, Eu, and Yb.