Search query: structural and bonding changes in cesium iodide at high pressure

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abstract: Cesium iodide, a simple ionic salt at low pressures, undergoes a second order transformation at 40 gigapascals (400 kilobars) from the cubic B2 (cesium chloride type) structure to the body centered tetragonal structure. Also, the energy gap between valence and conduction bands decreases from 6.4 electron volts at zero pressure to about 1.7 electron volts at 60 gigapascals, transforming cesium iodide from a highly ionic compound to a semiconductor. The structural transition increases the rate at which the band gap closes, and an extrapolation suggests that cesium iodide becomes metallic near (or somewhat above) 100 gigapascals. Similar changes in bonding character are likely to occur in other alkali halides at pressures above 100 gigapascals.
author_names: Elise Barbara Knittle

Raymond Jeanloz
title: Structural and Bonding Changes in Cesium Iodide at High Pressures
venue: Science
year: 1984

abstract: Ying Xu,1 John S. Tse,1,2 Artem R. Oganov,3,4 Tian Cui,1 Hui Wang,1 Yanming Ma,1, and Guangtian Zou1 1National Lab of Superhard Materials, Jilin University, Changchun 130012, People's Republic of China 2Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5E2 3Department of Materials, Laboratory of Crystallography, ETH Zurich, HCI G 515, Wolfgang Pauli Strasse 10, CH 8093 Zurich, Switzerland 4Department of Geology, Moscow State University, 119992 Moscow, Russia Received 2 March 2009; published 8 April 2009
author_names: Ying Xu

John S Tse

Artem R Oganov

Tian Cui

Hui Wang

Yanming Ma

Guang-tian Zou
title: Superconducting high pressure phase of cesium iodide
year: 2009

abstract: A broad organic inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH3NH3( or formamidinium (HC(NH2)2( cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X ray diffraction analysis of 1 4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature dependent single crystal X ray diffraction in the 100 400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid IR region that display characteristic absorption features. Temperature dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1 4 behave as direct gap semiconductors with energy band gaps distributed in the range of 1.25 1.75 eV. The compounds exhibit an intense near IR photoluminescence (PL) emission in the 700 1000 nm range (1.1 1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH3NH3Sn(1 x)Pb(x)I3 (5) The charge transport type in these materials was characterized by Seebeck coefficient and Hall effect measurements. The compounds behave as p or n type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are n type; p type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compounds, there is a facile tendency toward oxidation which causes the materials to be doped with Sn(4+ and thus behave as p type semiconductors displaying metal like conductivity. The compounds appear to possess very high estimated electron and hole mobilities that exceed 2000 cm(2)(V s) and 300 cm(2)(V s) respectively, as shown in the case of CH3NH3SnI3 (1) We also compare the properties of the title hybrid materials with those of the "all inorganic" CsSnI3 and CsPbI3 prepared using identical synthetic methods.
author_names: Constantinos C Stoumpos

Christos D Malliakas

Mercouri G Kanatzidis
title: Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near infrared photoluminescent properties.
venue: Inorganic chemistry
year: 2013

abstract: Radioactive Cs and I ions are the products of uranium fission, and can be easily dissolved in water during an accident at a nuclear reactor, such as those that occurred at Chernobyl in 1986, at Three Mile Island in Pennsylvania in 1979, and in 2011 at Fukushima, Japan. In 2009, leaks of radioactive materials such as Cs and I isotopes also occurred during minor accidents at nuclear power stations in Britain, Germany, and the U.S. These leaks have raised concerns about exposure levels in the nearby communities because it is feared that these fission products could make their way into the food chain when present in waste water. Radioactive iodine is also used in the treatment of thyroid cancer, and, as a result, radioactive wastewater is discharged by a large number of medical research institutions. The wide use of radioisotopes requires effective methods to manage radioactive waste, and methods currently used are complex and extremely costly. Herein we demonstrate a potentially cost effective method to remediate Cs and I ions from contaminated water by using the unique chemistry of titanate nanotubes and nanofibers, which can not only chemisorb these ions but efficiently trap them for safe disposal. Inorganic cation exchangers, such as crystalline silicotitanates, zeolites, clay minerals, layered Zr phosphates, and layered sulfide frameworks, have been studied for separation of Cs ions from nuclear wastewater and safe disposal of the exchanged cations because of the ability of these exchangers to withstand intense radiation and elevated temperatures, in addition to their high ion exchange capacity. Because ion exchange in materials is usually a reversible process, except in micas, the radioactive ions in the exchanger may be released to water. Titanates are refractory mineral substances that are very stable with respect to radiation and chemical, thermal, and mechanical changes. Titanate nanofibers and nanotubes (with chemical formula Na2Ti3O7) can be easily synthesized at low cost under hydrothermal conditions. These materials possess a layered structure in which TiO6 octahedra are the basic structural units (Figure S1 in the Supporting Information) These layers carry negative charges and are approximately two oxygen atoms thick. Na ions are situated between the layers and can be exchanged with other cations. In the present study, we show how trititanate nanofibers (T3NF) and nanotubes (T3NT) can be used to efficiently remove radioactive Cs ions from aqueous solution by cation exchange. Figure 1a shows that the nanotubular T3NT can remove 80% of Cs ions from solutions with Cs concentrations up to 250 ppm. The ions can be completely removed when the Cs ion concentration is below 80 ppm. In contrast, the fibril T3NF has a comparatively lower absorption capacity than
author_names: Dongjiang Yang

Sarina Sarina

Huaiyong Zhu

Hongwei Liu

Zhanfeng Zheng

Mengxia Xie

Suzanne V Smith

Sridhar Komarneni
title: Capture of radioactive cesium and iodide ions from water by using titanate nanofibers and nanotubes.
venue: Angewandte Chemie
year: 2011

abstract: Radioactive fallout Cs (cesium 137) deposited across the landscape from atmospheric nuclear tests is strongly absorbed on soil particles limiting its movement by chemical and biological processes. Most Cs movement in the environment is by physical processes; therefore, Cs is a unique tracer for studying erosion and sedimentation. Cesium 137 loss from a watershed has been shown to correlate strongly with soil loss calculated by the Universal Soil Loss Equation (USLE) or measured from small runoff plates. By measuring spatial patterns of Cs in vertical and horizontal planes across the landscape, rates of soil loss or deposition can be measured for different parts of a watershed. Even within landscape units, redistribution of soil can be mapped and erosion or deposition rates for different parts of individual fields measured and mapped. Sediment accumulation rates can be measured by comparing the vertical distribution of Cs in sediments with the temporal deposition of fallout Cs from the atmosphere to locate sediment horizons. Using these dated sediment horizons, sediment accumulation rates can be measured. Interpretations about the location of these dated horizons must consider particle size of the sediments, reworking of deposited sediments, diffusional movement of Cs, and time rates of physical process in the sedimentation process. The Cs technique can be used to determine sediment accumulation rates in a wide variety of depositional environments including reservoirs, lakes, wetlands, coastal areas, and floodplains. The bibliography shows that Cs has been used widely for studying erosion and sedimentation in many different environments around the world.
author_names: Jerry C Ritchie

J Roger Mchenry
title: Application of Radioactive Fallout Cesium 137 for Measuring Soil Erosion and Sediment Accumulation Rates and Patterns: A Review
year: 1990

abstract: Colloidal nanocrystals (NCs) of APbX3 type lead halide perovskites [A Cs+ CH3NH3+ (methylammonium or MA+ or CH(NH2)2+ (formamidinium or FA+ X Cl Br I have recently emerged as highly versatile photonic sources for applications ranging from simple photoluminescence down conversion (e.g. for display backlighting) to light emitting diodes. From the perspective of spectral coverage, a formidable challenge facing the use of these materials is how to obtain stable emissions in the red and infrared spectral regions covered by the iodide based compositions. So far, red emissive CsPbI3 NCs have been shown to suffer from a delayed phase transformation into a nonluminescent, wide band gap 1D polymorph, and MAPbI3 exhibits very limited chemical durability. In this work, we report a facile colloidal synthesis method for obtaining FAPbI3 and FA doped CsPbI3 NCs that are uniform in size (10 15 nm) and nearly cubic in shape and exhibit drastically higher robustness than their MA or Cs only cousins with similar sizes and morphologies. Detailed structural analysis indicated that the FAPbI3 NCs had a cubic crystal structure, while the FA0.1Cs0.9PbI3 NCs had a 3D orthorhombic structure that was isostructural to the structure of CsPbBr3 NCs. Bright photoluminescence (PL) with high quantum yield (QY 70% spanning red (690 nm, FA0.1Cs0.9PbI3 NCs) and near infrared (near IR, ca. 780 nm, FAPbI3 NCs) regions was sustained for several months or more in both the colloidal state and in films. The peak PL wavelengths can be fine tuned by using postsynthetic cation and anion exchange reactions. Amplified spontaneous emissions with low thresholds of 28 and 7.5 mJ cm 2 were obtained from the films deposited from FA0.1Cs0.9PbI3 and FAPbI3 NCs, respectively. Furthermore, light emitting diodes with a high external quantum efficiency of 2.3% were obtained by using FAPbI3 NCs.
author_names: Loredana Protesescu

Sergii Yakunin

Sudhir Kumar

Janine Baer

Federica Bertolotti

Norberto Masciocchi

Antonietta Guagliardi

Matthias J Grotevent

Ivan Shorubalko

Maryna I Bodnarchuk

Chih-Jen Shih

Maksym V Kovalenko
title: Dismantling the "Red Wall" of Colloidal Perovskites: Highly Luminescent Formamidinium and Formamidinium Cesium Lead Iodide Nanocrystals
venue: ACS nano
year: 2017

abstract: We present the photoelectron spectra of negatively charged cesium iodide nanocrystals recorded using 2.540 eV photons. The species examined were produced using an inert gas condensation cluster ion source, and they ranged in size from (CsI) n=13 to nanocrystal anions comprised of 330 atoms. Nanocrystals showing two distinct types of photoemission behavior were observed. For (CsI) n=13 and (CsI) n=36 165, a plot of cluster anion photodetachment threshold energies vs n 1/3 gives a straight line extrapolating (at n 1/3=0, i.e. n= to 2.2 eV, the photoelectric threshold energy for F centers in bulk cesium iodide. The linear extrapolation of the cluster anion data to the corresponding bulk property implies that the electron localization in these gas phase nanocrystals is qualitatively similar to that of F centers in extended alkali halide crystals. These negatively charged cesium iodide nanocrystals are thus shown to support embryonic forms of F centers, which mature with increasing cluster size toward conde.
author_names: Harry W Sarkas

Linda H Kidder

Kit H Bowen
title: Photoelectron spectroscopy of color centers in negatively charged cesium iodide nanocrystals
year: 1995

abstract: Cesium iodide (CsI) coated carbon fiber cathodes have shown promise as a cold cathode for microwave and x ray devices. In particular, the cathodes have demonstrated over 1 000 000 shots lifetime at operating voltages at or in excess of 165 kV and current densities greater than 25A/cm2. While the vacuum emission characteristics have been well studied, the materials characteristics of the cathodes themselves, particularly after operation, have received little attention. Furthermore, while researchers at University of Wisconsin have demonstrated a reduction in work function of carbon due to the CsI coating, the details of the emission mechanism remain poorly understood. This article gives results of a series of materials diagnostics investigating the cathode surface morphology as well as the changes in the carbon fiber structure with cathode shot history. We demonstrate that the cathode surface undergoes several changes in relation to the bond line along the fiber substrate interface as well as at the fiber
author_names: Donald A Shiffler

Susan L Heidger

Keith L Cartwright

Richard A Vaia

David Charles Liptak

Gary E Price

M Lacour

Ken Golby
title: Materials characteristics and surface morphology of a cesium iodide coated carbon velvet cathode
year: 2008

abstract: Although known since the late 19th century, organic inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. This review will explore beyond the current focus on three dimensional (3 D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3 D and lower dimensional organic based perovskite family for electronic, optical, and energy based applications as well as fundamental research. The concept of a multifunctional organic inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.
author_names: Bayrammurad Saparov

David B Mitzi
title: Organic Inorganic Perovskites: Structural Versatility for Functional Materials Design.
venue: Chemical reviews
year: 2016

abstract: Thermophilic organisms flourish in varied high temperature environmental niches that are deadly to other organisms. Recently, genomic evidence has implicated a critical role for disulfide bonds in the structural stabilization of intracellular proteins from certain of these organisms, contrary to the conventional view that structural disulfide bonds are exclusively extracellular. Here both computational and structural data are presented to explore the occurrence of disulfide bonds as a protein stabilization method across many thermophilic prokaryotes. Based on computational studies, disulfide bond richness is found to be widespread, with thermophiles containing the highest levels. Interestingly, only a distinct subset of thermophiles exhibit this property. A computational search for proteins matching this target phylogenetic profile singles out a specific protein, known as protein disulfide oxidoreductase, as a potential key player in thermophilic intracellular disulfide bond formation. Finally, biochemical support in the form of a new crystal structure of a thermophilic protein with three disulfide bonds is presented together with a survey of known structures from the literature. Together, the results provide insight into biochemical specialization and the diversity of methods employed by organisms to stabilize their proteins in exotic environments. The findings also motivate continued efforts to sequence genomes from divergent organisms.
author_names: Morgan Beeby

Brian D O'Connor

Carsten Ryttersgaard

Daniel R Boutz

L Jeanne Perry

Todd O Yeates
title: The Genomics of Disulfide Bonding and Protein Stabilization in Thermophiles
venue: PLoS biology
year: 2005