Exchange interactions in polynuclear transition metal complexes. Structural properties of cesium tribromocuprate(II), CsCuBr3, a strongly coupled copper(II) system

High-entropy alloy screening for halide perovskites

As the concept of high-entropy alloying (HEA) extends beyond metals, new materials screening methods are needed. Halide perovskites (HP) are a prime case study because greater stability is needed for photovoltaics applications, and there are 322 experimentally observed HP end-members, which leads to more than 1057 potential alloys. We screen HEAHP by first calculating the configurational entropy of 106 equimolar alloys with experimentally observed end-members. To estimate enthalpy at low computational cost, we turn to the delta-lattice parameter approach, a well-known method for predicting III-V alloy miscibility. To generalize the approach for non-cubic crystals, we introduce the parameter of unit cell volume coefficient of variation (UCV), which does a good job of predicting the experimental HP miscibility data. We use plots of entropy stabilization versus UCV to screen promising alloys and identify 102 HEAHP of interest.

Optical Sensing Capability Evaluation for Methylammonium Based Perovskites for Explosive

Here, we have synthesized methylammonium based two metal halide perovskites (MHP) such as MAPbBr3, and MAPbI3 using methylammonium bromide, methylammonium iodide, lead bromide, respective at room temperature under certain experimental conditions. All synthesized MHPs have been confirmed through X-ray diffraction technique (XRD), scanning electron microscope (SEM), Fourier transform infra-red (FTIR) and photoluminescence (PL) analysis. Afterward, comparative evaluation on optical sensing capability has been made for both MHPs using PL in different solvents. Importantly, we find out that MAPbBr3 exhibit an excellent optical feature over MAPbI3 in hexane only. Afterward, MAPbBr3 has also been explored to know the sensing capability for nitrobenzene sensing. Our model study confirms that MAPbBr3 is an excellent sensing material with R square (0.87), selectivity (16.9%) and Stern Volmer constant (Ksv=10- 2 × 0.464) for nitrobenzene in hexane.

Electronic Modulation in Site-Selective Occupation of Quasi-2D Triangular-Lattice Cs2CuCl4-xBrx Perovskite Probed by Surface-Sensitive Characterization

A controllable electronic manipulation in a frustrated magnetic system such as solution-based two-dimensional (2D) all-inorganic perovskites offers a possible route for their integrations with electronic and magnetic devices for their advanced applications. Here, we perform element-specific investigations of an emergent class of quasi-2D all-inorganic perovskites Cs₂CuCl_4-xBr_x with (0 ≤ x ≤ 4) using a combination of synchrotron-radiation photoelectron techniques. Surface- and element-sensitive X-ray absorption spectroscopy spectra of Cu L_2,3 edges indicate strong electronic transition that is largely influenced by their halogen content at room temperature. This implies that site-selective occupation largely dominates the electronic transition across the unoccupied states of these series since chlorine atoms possess a stronger electronegative character than bromine atoms. Moreover, the implication of halogen site is reflected in the valence band of Cl-rich copper perovskite in which the valence band edge is closer to Fermi energy (E_F) than that of the Br-rich compound. Furthermore, X-ray magnetic circular dichroism spectra of mixed ratio and Br-rich compounds exhibit antiferromagnetism at room temperature. These site-specific magnetic-spectroscopic results are corroborated by density functional theory calculations. The strong electronic modulation and the local magnetic spectroscopy results in these solution-based and low-temperature-growth materials will pave the way toward energy- and cost-efficient perovskite devices.

ℇ-RbCuCl3, a new polymorph of rubidium copper trichloride: synthesis, structure and structural complexity

A novel polymorph of RbCuCl₃ (rubidium copper trichloride), denoted ℇ-RbCuCl₃, has been prepared by chemical vapour transport (CVT) from a mixture of CuO, CuCl₂, SeO₂ and RbCl. The new polymorph crystallizes in the orthorhombic space group C222₁. The crystal structure is based on an octahedral framework of the 4H perovskite type. The Rb⁺ and Cl^- ions form a four-layer closest-packing array with an ABCB sequence. The Cu²⁺ cations reside in octahedral cavities with a typical [4 + 2]-Jahn-Teller-distorted coordination, forming four short and two long Cu-Cl bonds. ℇ-RbCuCl₃ is the most structurally complex and most dense among all currently known RbCuCl₃ polymorphs, which allows us to suggest that it is a high-pressure phase, which is unstable under ambient conditions.

All-inorganic Cs2CuX4 (X = Cl, Br, and Br/I) perovskite quantum dots with blue-green luminescence

Lead-free, all-inorganic copper based perovskite Cs₂CuX₄ (X = Cl, Br, and Br/I) quantum dots were synthesized and investigated for the first time.

New strontium polysulfides, SrS3, and Sr2(OH)2S4.10H2O, obtained by the high-pressure treatment of a Sr-S mixture

A new polymorph of SrS(3) was obtained by a reaction of SrS and S with an atomic ratio of Sr:S = 1:5 under a pressure of 5 GPa at 1200 degrees C. It crystallized in a tetragonal unit cell with a = 6.708(1) A, c = 3.942(1) A, and V = 177.36(6) A(3). It was isotypic with BaS(3), and contained S3(2-) polysulfide ions. The product obtained from the high-pressure synthesis contained an amorphous component. It was highly deliquescent and formed a yellowish solution. A new layered polysulfide, Sr(2)(OH)(2)S(4).10H(2)O, crystallized in the solution. The sulfide belonged to a triclinic space group of P (No. 2) with lattice constants of a = 5.9107(5) A, b = 7.8682(6) A, c = 9.4134(6) A, alpha = 75.639(6) degrees, beta = 73.824(3) degrees, gamma = 71.639(3) degrees, V = 392.83(5) A(3), and Z = 1. Each Sr ion was coordinated with one OH ligand and eight H(2)O ligands. Six H(2)O ligands out of the eight were bridging ligands to form two-dimensional [Sr(2)(OH)(2)(H(2)O)(10)(2+)]( infinity ) cationic layers, between which S4(2-) tetrapolysulfide ions were situated. The S4(2-) anion had a coplanar configuration with a dihedral angle of 180.0 degrees. The stability of S4(2-) anions having different conformations was discussed from a viewpoint of ab initio MO calculations on changing the dihedral angles of S4(2-).