High-Pressure Structural and Optical Studies of Pure Low-Dimensional Cesium Lead Chlorides CsPbCl and CsPbCl.

We report high-pressure single-crystal X-ray diffraction, optical absorption, and photoluminescence investigations of all-inorganic perovskite-related materials CsPbCl and CsPbCl. The crystal structure of CsPbCl, composed of alternate layers of Cs cations and Pb-Cl frameworks, is stable under pressure up to at least 4.2 GPa.

Dipole-Moment Modulation in New Incommensurate Ferrocene.

Despite 70 years of research on metallocenes and their applications, there are still unresolved regions in its phase diagram of the prototypic sandwich compound, ferrocene Fe[CH] (FeCp), and its molecular 5-fold symmetry cannot be reconciled with the dielectric response of this crystal. We found a new phase I″ of ferrocene, which reveals the relationships between the molecular conformation, intermolecular interactions, and electric permittivity of this compound. Between 172.

Thermodynamic Stability, Structure, and Optical Properties of Perovskite-Related CsPbBr Single Crystals under Pressure.

CsPbBr belongs to all inorganic perovskite-related quasi-two-dimensional materials that have attracted considerable attention due to their potential for optoelectronic applications. In this study, we solve numerous controversies on the physical properties of this material. We show that optical absorption in the visible spectrum and green photoluminescence are due to microcrystallites of the three-dimensional CsPbBr perovskite settled on the CsPbBr plates and that carefully cleaned crystal plates are devoid of these features.

Comment on "Improper molecular ferroelectrics with simultaneous ultrahigh pyroelectricity and figures of merit" by Li .

Li . (, 29 January, p. eabe3068) claim the discovery of two improper ferroelectrics, dabcoHClO and dabcoHBF (dabco = 1,4-diazabicyclo[2.

Material Parameters Identification of Historic Lighthouse Based on Operational Modal Analysis.

In the present paper, the identification of the material parameters of a masonry lighthouse is discussed. A fully non-invasive method was selected, in which the material properties were determined via numerical model validation applied to the first pair of natural frequencies and their related mode shapes, determined experimentally. The exact structural model was built by means of the finite element method.

Band Gap Engineering in MASnBr and CsSnBr Perovskites: Mechanistic Insights through the Application of Pressure.

Here we report on the first structural and optical high-pressure investigation of MASnBr (MA = [CHNH]) and CsSnBr halide perovskites. A massive red shift of 0.4 eV for MASnBr and 0.

Vitrification and New Phases in the Water:Pyrimidine Binary Eutectic System.

The binary diagram for pyrimidine:water mixtures has been determined by differential scanning calorimetry, in situ single-crystal, and powder X-ray diffraction experiments. The eutectic point has been located near the 1:4 n/n ratio at 234.5 K.

Differences in photoinduced optical transients in perovskite absorbers for solar cells.

Methylammonium lead iodide films and powdered crystals were studied by time-resolved absorption and emission spectroscopy on the time scales from femtoseconds to nanoseconds. Strikingly different transient absorption signals were observed, changing from strong long-wavelength band-edge bleach to weak signatures of band-shift, which depended on the absorber form (films or polycrystals) and preparation method (stoichiometric or non-stoichiometric). The observed differences were correlated with the variation in absorption and emission spectra, changes in photo-induced carrier lifetimes and solar cell efficiency.

Photovoltaic Hybrid Perovskites under Pressure.

High-pressure studies on methylammonium trihaloplumbates, of general formula [CHNH]PbX (abbreviated MAPbX, where X = Cl, Br, I), and its analogues shed new light on the materials for harvesting solar energy and open new perspectives for photovoltaic science and technology. However, there are considerable discrepancies between the reported structural, calorimetric, and spectroscopic results and even between the results obtained by the same technique, for example, of X-ray diffraction. The origins of these discrepancies and possible pitfalls in the diffraction and spectroscopic studies on MAPbX crystals have been investigated.

Mechanism of Pressure-Induced Phase Transitions, Amorphization, and Absorption-Edge Shift in Photovoltaic Methylammonium Lead Iodide.

Our single-crystal X-ray diffraction study of methylammonium lead triiodide, MAPbI3, provides the first comprehensive structural information on the tetragonal phase II in the pressure range to 0.35 GPa, on the cubic phase IV stable between 0.35 and 2.

Impact of structural differences in carcinopreventive agents indole-3-carbinol and 3,3'-diindolylmethane on biological activity. An X-ray, ¹H-¹⁴N NQDR, ¹³C CP/MAS NMR, and periodic hybrid DFT study.

Three experimental techniques (1)H-(14)N NQDR, (13)C CP/MAS NMR and X-ray and Density Functional Theory (GGA/BLYP with PBC) and Hirshfeld surfaces were applied for the structure-activity oriented studies of two phyto-antioxidants and anticarcinogens: indole-3-carbinol, I3C, and 3,3'-diindolylmethane, DIM, (its bioactive metabolite). One set of (14)N NQR frequencies for DIM (2.310, 2.

Comment on the phase transition mechanism in diglycine methanesulfonate.

The transition mechanism revised: The transition in diglycine methanesulfonate at 133 K has an order-disorder character. It has been evidenced that the previously postulated by Zhou and coworkers (Chem. Asian J.

Crystal structures, phase transitions, and pressure-induced ferroelectricity in [C(NH2)3]5SO4(SO3-OC2H5)2F.

A guanidinium compound, [C(NH(2))(3)](5)SO(4)(SO(3)-OC(2)H(5))(2)F, with complex anionic sublattice has been synthesized and characterized by calorimetric and dielectric measurements at ambient and high hydrostatic pressures, as well as by single-crystal X-ray diffraction at varied temperatures. At room temperature, the crystal structure is orthorhombic, with the space group Pnma. In this phase, each of the two crystallographically nonequivalent ethoxysulfonate anions is disordered between two sites.

Simple guanidinium salts revisited: room-temperature ferroelectricity in hydrogen-bonded supramolecular structures.

Dielectric, calorimetric, and X-ray diffraction methods have been employed to characterize the crystals of guanidinium tetrafluoroborate and guanidinium perchlorate, both built of two-dimensional honeycomb hydrogen-bonded sheets. The room-temperature ferroelectricity of these isosymmetric complexes (space group R3m) has been evidenced by the polarization switching in an external electric field and pyroelectric effect. The analysis of structural data as a function of temperature showed that the high values of spontaneous polarization of about 8.

Pressure-induced collapse of guanidinium nitrate N-H···O bonded honeycomb layers into a 3-D pattern with varied H-acceptor capacity.

Highly favoured N-H···O bonded honeycomb layers in guanidinium nitrate, C(NH(2))(3)(+)NO(3)(-), have been destabilized by a pressure of 0.6 GPa, and the novel motif of 3-dimensional N-H···O bonded aggregation in high-pressure phase IV determined for in situ grown single-crystal by X-ray diffraction. The mechanism of the transition involves the collapse of voids present in phases I, II and III.

Bias-field and pressure effects on the one-dimensional dielectric response in N-H(+)...N hydrogen-bonded 1,4-diazabicyclo[2.2.2]octane hydrobromide crystal.

Unusual dielectric properties of 1,4-diazabicyclo[2.2.2]octane hydrobromide [C(6)H(13)N(2)](+).

Anomalous protonic-glass evolution from ordered phase in NH...N hydrogen-bonded dabcoHBF4 ferroelectric.

Dielectric properties, spontaneous polarization, and phase transitions of the NH+...

Giant dielectric anisotropy and relaxor ferroelectricity induced by proton transfers in NH+...N-bonded supramolecular aggregates.

A huge dielectric effect has been observed in a pure and water-soluble hydrogen-bonded organic crystal, 1,4-diazabicyclo[2.2.2]octane hydroiodide [C6H13N2]+.

From nonpolar to ferroelectric crystal structure: the temperature-tuned growth of two guanidinium ethoxysulfonate polymorphs.

Guanidinium ethoxysulfonate, [C(NH2)3]+[C2H5O-SO3]-, was synthesized, and two polymorphs, both stable at normal conditions, were grown from an aqueous solution by only a slight change in the crystallization temperature. The nonpolar polymorph I is built of hydrogen-bonded bilayers, while the ferroelectric polymorph II consists of single-layers. The diversity in the crystals' architecture and properties originates from the excessive number of proton-acceptor sites.

Disproportionation of pyrazine in NH+...N hydrogen-bonded complexes: new materials of exceptional dielectric response.

Centrosymmetric pyrazinium NH+...

Molecular interactions in crystalline dibromomethane and diiodomethane, and the stabilities of their high-pressure and low-temperature phases.

Dibromomethane, CH2Br2, and diiodomethane, CH2I2, have been in situ pressure-crystallized in a diamond-anvil cell and their structures determined by single-crystal X-ray diffraction at 0.61 and 0.16 GPa, respectively.

Structural implications of anomalous thermal expansion and glass-like dielectric response in pyridinium halogenoaurates.

The crystals of [C(5)NH(6)](+)[AuCl(4)](-), [C(5)NH(6)](+)[AuBr(4)](-), and [C(5)NH(6)](+)[AuI(4)](-) have been studied by single-crystal X-ray diffraction and dielectric spectroscopy. The structures of the chloride and bromide are isosymmetric, with the monoclinic space group C2/m, and both are built of sheets of pyridinium cations and tetrahalogenoaurate anions alternately arranged in the direction [001]. The anomalous thermal expansion and dielectric response characteristic of dipolar glass formation observed in these compounds have been interpreted in terms of the development of the short-range dipolar order and the competition between the ferroelectric and antiferroelectric interactions.

Ferroelectric order of parallel bistable hydrogen bonds.

A new NH.N hydrogen-bonded ferroelectric crystal of [C6H12N2H]+ReO - 4 (dabcoHReO4) exhibits exceptional dielectric properties that result from the unique structure where all the bistable NH..