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Crystal Growth & Design

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https://www.readbyqxmd.com/read/28615995/additive-enhanced-creeping-of-sodium-chloride-crystals
#1
Eleanor R Townsend, Willem J P van Enckevort, Jan A M Meijer, Elias Vlieg
This article investigates the mechanism behind the creeping of sodium chloride induced by additives. Here, an experimental approach is complemented with theoretical considerations to describe how creeping patterns of brine evolve and how the introduction of additives into the solution affects the morphology of the resultant crystals. We have found that these additives cause kinetic roughening and morphological instability mainly due to the reduction of surface free energy. There was also a marked increase in three-dimensional nucleation of the NaCl crystals and thus branching...
June 7, 2017: Crystal Growth & Design
https://www.readbyqxmd.com/read/28670205/why-do-hydrates-solvates-form-in-small-neutral-organic-molecules-exploring-the-crystal-form-landscapes-of-the-alkaloids-brucine-and-strychnine
#2
Doris E Braun, Ulrich J Griesser
Computational methods were used to generate and explore the crystal structure landscapes of the two alkaloids strychnine and brucine. The computed structures were analyzed and rationalized by correlating the modelling results to a rich pool of available experimental data. Despite their structural similarity, the two compounds show marked differences in the formation of solid forms. For strychnine only one anhydrous form is reported in the literature and two new solvates from 1,4-dioxane were detected in the course of this work...
November 2, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/28261000/a-versatile-system-for-high-throughput-in-situ-x-ray-screening-and-data-collection-of-soluble-and-membrane-protein-crystals
#3
Jana Broecker, Viviane Klingel, Wei-Lin Ou, Aidin R Balo, David J Kissick, Craig M Ogata, Anling Kuo, Oliver P Ernst
In recent years, in situ data collection has been a major focus of progress in protein crystallography. Here, we introduce the Mylar in situ method using Mylar-based sandwich plates that are inexpensive, easy to make and handle, and show significantly less background scattering than other setups. A variety of cognate holders for patches of Mylar in situ sandwich films corresponding to one or more wells makes the method robust and versatile, allows for storage and shipping of entire wells, and enables automated crystal imaging, screening, and goniometer-based X-ray diffraction data-collection at room temperature and under cryogenic conditions for soluble and membrane-protein crystals grown in or transferred to these plates...
November 2, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27829821/enhanced-nmr-discrimination-of-pharmaceutically-relevant-molecular-crystal-forms-through-fragment-based-ab-initio-chemical-shift-predictions
#4
Joshua D Hartman, Graeme M Day, Gregory J O Beran
Chemical shift prediction plays an important role in the determination or validation of crystal structures with solid-state nuclear magnetic resonance (NMR) spectroscopy. One of the fundamental theoretical challenges lies in discriminating variations in chemical shifts resulting from different crystallographic environments. Fragment-based electronic structure methods provide an alternative to the widely used plane wave gauge-including projector augmented wave (GIPAW) density functional technique for chemical shift prediction...
November 2, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/28670204/stoichiometric-and-non-stoichiometric-hydrates-of-brucine
#5
Doris E Braun, Ulrich J Griesser
The complex interplay of temperature and water activity (aw) / relative humidity (RH) on the solid form stability and transformation pathways of three hydrates (HyA, HyB and HyC), an isostructural dehydrate (HyAdehy ), an anhydrate (AH) and amorphous brucine has been elucidated and the transformation enthalpies quantified. The dihydrate (HyA) shows a non-stoichimetric (de)hydration behavior at RH < 40% at 25 °C and the removal of the water molecules results in an isomorphic dehydrate structure. The metastable dehydration product converts to AH upon storage at driest conditions or to HyA if exposed to moisture...
October 5, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27512345/role-of-caco3%C3%A2-neutral-pair-in-calcium-carbonate-crystallization
#6
Damiano Genovese, Marco Montalti, Fermín Otálora, Jaime Gómez-Morales, María Sancho-Tomás, Giuseppe Falini, Juan Manuel García-Ruiz
The molecular structure of the units that get incorporated into the nuclei of the crystalline phase and sustain their growth is a fundamental issue in the pathway from a supersaturated solution to the formation of crystals. Using a fluorescent dye we have recorded the variation of the pH value in time along a gel where CaCl2 and NaHCO3 counter-diffuse to crystallize CaCO3. The same pH-space-time distribution maps were also computationally obtained using a chemical speciation code (phreeqc). Using data arising from this model we investigated the space-time evolution of the activity of the single species (ions and ion pairs) involved in the crystallization process...
August 3, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27418882/surface-induced-phase-of-tyrian-purple-6-6-dibromoindigo-thin-film-formation-and-stability
#7
Magdalena Truger, Otello M Roscioni, Christian Röthel, Dominik Kriegner, Clemens Simbrunner, Rizwan Ahmed, Eric D Głowacki, Josef Simbrunner, Ingo Salzmann, Anna Maria Coclite, Andrew O F Jones, Roland Resel
The appearance of surface-induced phases of molecular crystals is a frequently observed phenomenon in organic electronics. However, despite their fundamental importance, the origin of such phases is not yet fully resolved. The organic molecule 6,6'-dibromoindigo (Tyrian purple) forms two polymorphs within thin films. At growth temperatures of 150 °C, the well-known bulk structure forms, while at a substrate temperature of 50 °C, a surface-induced phase is observed instead. In the present work, the crystal structure of the surface-induced polymorph is solved by a combined experimental and theoretical approach using grazing incidence X-ray diffraction and molecular dynamics simulations...
July 6, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/28663717/computational-and-experimental-characterization-of-five-crystal-forms-of-thymine-packing-polymorphism-polytypism-disorder-and-stoichiometric-0-8-hydrate
#8
Doris E Braun, Thomas Gelbrich, Klaus Wurst, Ulrich J Griesser
New polymorphs of thymine emerged in an experimental search for solid forms, which was guided by the computationally generated crystal energy landscape. Three of the four anhydrates (AH) are homeoenergetic (A° - C) and their packing modes differ only in the location of oxygen and hydrogen atoms. AHs A° and B are ordered phases, whereas AH C shows disorder (X-ray diffuse scattering). Anhydrates AHs A° and B are ordered phases, whereas AH C shows disorder (X-ray diffuse scattering). Analysis of the crystal energy landscape for alternative AH C hydrogen bonded ribbon motifs identified a number of different packing modes, whose 3D structures were calculated to deviate by less than 0...
June 1, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27175105/crystallization-of-carbamazepine-in-proximity-to-its-precursor-iminostilbene-and-a-silica-surface
#9
Paul Christian, Christian Röthel, Martin Tazreiter, Andreas Zimmer, Ingo Salzmann, Roland Resel, Oliver Werzer
Amorphous films of the anticonvulsant drug carbamazepine are easily accessible by various methods, while the crystallization into specific polymorphs represents a challenging and time-consuming task. In this work, the crystallization of drop cast carbamazepine at silica surfaces is investigated by atomic force microscopy and both in situ and ex situ grazing incidence X-ray diffraction. The pristine films grow with low crystallization rates into a triclinic polymorph, exhibiting poor orientational order within films...
May 4, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27175104/detergent-mediated-formation-of-%C3%AE-hematin-heme-crystallization-promoted-by-detergents-implicates-nanostructure-formation-for-use-as-a-biological-mimic
#10
Rebecca D Sandlin, Kim Y Fong, Renata Stiebler, Christopher P Gulka, Jenny E Nesbitt, Matheus P Oliveira, Marcus F Oliveira, David W Wright
Hemozoin is a unique biomineral that results from the sequestration of toxic free heme liberated as a consequence of hemoglobin degradation in the malaria parasite. Synthetic neutral lipid droplets (SNLDs) and phospholipids were previously shown to support the rapid formation of β-hematin, abiological hemozoin, under physiologically relevant pH and temperature, though the mechanism by which heme crystallization occurs remains unclear. Detergents are particularly interesting as a template because they are amphiphilic molecules that spontaneously organize into nanostructures and have been previously shown to mediate β-hematin formation...
May 4, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27081373/supramolecular-synthons-will-giant-rigid-superspheres-do
#11
Eugenia Peresypkina, Alexander Virovets, Manfred Scheer
For the first time, the concept of supramolecular synthons was applied to giant rigid superspheres based on pentaphosphaferrocene [Cp(R)Fe(η(5)-P5)] (R = Me, Et) and Cu(I) halides, which reach 2.1-3.0 nm in diameter. Two supramolecular synthons, σ-π and π-π, are discovered based on halogen···Cp(R) and Cp*···Cp* specific interactions, respectively. The geometry of the synthons is reproducible in a series of crystal structures of various supramolecules. The σ-π synthon alone is realized more frequently for Br-containing superspheres...
April 6, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27065755/self-assembled-multilayers-of-silica-nanospheres-for-defect-reduction-in-non-and-semipolar-gallium-nitride-epitaxial-layers
#12
Tongtong Zhu, Tao Ding, Fengzai Tang, Yisong Han, Muhammad Ali, Tom Badcock, Menno J Kappers, Andrew J Shields, Stoyan K Smoukov, Rachel A Oliver
Non- and semipolar GaN have great potential to improve the efficiency of light emitting devices due to much reduced internal electric fields. However, heteroepitaxial GaN growth in these crystal orientations suffers from very high dislocation and stacking faults densities. Here, we report a facile method to obtain low defect density non- and semipolar heteroepitaxial GaN via selective area epitaxy using self-assembled multilayers of silica nanospheres (MSN). Nonpolar (11-20) and semipolar (11-22) GaN layers with high crystal quality have been achieved by epitaxial integration of the MSN and a simple one-step overgrowth process, by which both dislocation and basal plane stacking fault densities can be significantly reduced...
February 3, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/26834509/surface-reconstructions-in-organic-crystals-simulations-of-the-effect-of-temperature-and-defectivity-on-bulk-and-001-surfaces-of-2-2-6-2%C3%A2-ternaphthalene
#13
Mosè Casalegno, Massimo Moret, Roland Resel, Guido Raos
2,2':6',2″-Ternaphthalene (NNN) is a novel, blue-emitting material, suitable for preparation of organic light-emitting diodes. Its crystal structure has been solved recently, but its thermal behavior and surface properties have not yet been explored, partly due to the difficulty in obtaining high quality crystals. In the present study we use classical molecular dynamics to investigate the thermal behavior of bulk and (001) surfaces of NNN. Our bulk simulations indicate the occurrence of a phase transition at about 600 K...
January 6, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/26823658/mechanism-of-rare-earth-incorporation-and-crystal-growth-of-rare-earth-containing-type-i-clathrates
#14
Andrey Prokofiev, Robert Svagera, Monika Waas, Matthias Weil, Johannes Bernardi, Silke Paschen
Type-I clathrates possess extremely low thermal conductivities, a property that makes them promising materials for thermoelectric applications. The incorporation of cerium into one such clathrate has recently been shown to lead to a drastic enhancement of the thermopower, another property determining the thermoelectric efficiency. Here we explore the mechanism of the incorporation of rare earth elements into type-I clathrates. Our investigation of the crystal growth and the composition of the phase Ba8-x RE x TM y Si46-y (RE = rare earth element; TM = Au, Pd, Pt) reveals that the RE content x is mainly governed by two factors, the free cage space and the electron balance...
January 6, 2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27891066/in-situ-evaluation-of-calcium-phosphate-nucleation-kinetics-and-pathways-during-intra-and-extrafibrillar-mineralization-of-collagen-matrices
#15
Doyoon Kim, Byeongdu Lee, Stavros Thomopoulos, Young-Shin Jun
We revealed that nucleation sites within collagen fibrils determined pathways for calcium phosphate (CaP) nucleation and its transformation, from amorphous species to crystalline plates, during the biomineralization process. Using in situ small-angle X-ray scattering (SAXS), we examined the nucleation and growth of CaP within collagen matrices and elucidated how a nucleation inhibitor, polyaspartic acid (pAsp), governs mineralization kinetics and pathways at multiple length scales. Mineralization without pAsp led initially to spherical aggregates of CaP in the entire extrafibrillar spaces...
2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/27683240/protein-crystallization-in-an-actuated-microfluidic-nanowell-device
#16
Bahige G Abdallah, Shatabdi Roy-Chowdhury, Raimund Fromme, Petra Fromme, Alexandra Ros
Protein crystallization is a major bottleneck of structure determination by X-ray crystallography, hampering the process by years in some cases. Numerous matrix screening trials using significant amounts of protein are often applied, while a systematic approach with phase diagram determination is prohibited for many proteins that can only be expressed in small amounts. Here, we demonstrate a microfluidic nanowell device implementing protein crystallization and phase diagram screening using nanoscale volumes of protein solution per trial...
2016: Crystal Growth & Design
https://www.readbyqxmd.com/read/26494983/phase-transformation-in-radially-merged-wurtzite-gaas-nanowires
#17
Daniel Jacobsson, Fangfang Yang, Karla Hillerich, Filip Lenrick, Sebastian Lehmann, Dominik Kriegner, Julian Stangl, L Reine Wallenberg, Kimberly A Dick, Jonas Johansson
III-V Nanowires (NWs) grown with metal-organic chemical vapor deposition commonly show a polytypic crystal structure, allowing growth of structures not found in the bulk counterpart. In this paper we studied the radial overgrowth of pure wurtzite (WZ) GaAs nanowires and characterized the samples with high resolution X-ray diffraction (XRD) to reveal the crystal structure of the grown material. In particular, we investigated what happens when adjacent WZ NWs radially merge with each other by analyzing the evolution of XRD peaks for different amounts of radial overgrowth and merging...
October 7, 2015: Crystal Growth & Design
https://www.readbyqxmd.com/read/26435703/control-of-assembly-of-dihydropyridyl-and-pyridyl-molecules-via-directed-hydrogen-bonding
#18
Jian Lü, Li-Wei Han, Nada H Alsmail, Alexander J Blake, William Lewis, Rong Cao, Martin Schröder
The crystallization of two dihydropyridyl molecules, 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)benzene ([C40H24N10]·2DMF, 1·2DMF; DMF = dimethylformamide) and 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)phenylbenzene ([C46H28N10]·2DMF, 3·2DMF), and their respective oxidized pyridyl analogues, 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)benzene ([C40H20N10], 2) and 1,4-bis(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)phenylbenzene ([C46H24N10]·DMF, 4·DMF), has been achieved under solvothermal conditions...
September 2, 2015: Crystal Growth & Design
https://www.readbyqxmd.com/read/26366128/surface-induced-polymorphism-as-a-tool-for-enhanced-dissolution-the-example-of-phenytoin
#19
Daniela Reischl, Christian Röthel, Paul Christian, Eva Roblegg, Heike M A Ehmann, Ingo Salzmann, Oliver Werzer
Polymorphism and morphology can represent key factors tremendously limiting the bioavailability of active pharmaceutical ingredients (API), in particular, due to solubility issues. Within this work, the generation of a yet unknown surface-induced polymorph (SIP) of the model drug, 5,5-diphenylimidazolidin-2,4-dion (phenytoin), is demonstrated in thin films through altering the crystallization kinetics and the solvent type. Atomic force microscopy points toward the presence of large single-crystalline domains of the SIP, which is in contrast to samples comprising solely the bulk phase, where extended dendritic phenytoin networks are observed...
September 2, 2015: Crystal Growth & Design
https://www.readbyqxmd.com/read/26366127/complex-behavior-of-caffeine-crystallites-on-muscovite-mica-surfaces
#20
Christian Röthel, Michal Radziown, Roland Resel, Andreas Zimmer, Clemens Simbrunner, Oliver Werzer
Defined fabrication of organic thin films is highly desired in technological, as well as pharmaceutical, applications since morphology and crystal structure are directly linked to physical, electrical, and optical properties. Within this work, the directed growth of caffeine deposited by hot wall epitaxy (HWE) on muscovite mica is studied. Optical and atomic force microscopy measurements reveal the presence of caffeine needles exhibiting a preferable alignment in the azimuthal directions with respect to the orientation of the defined mica surface...
September 2, 2015: Crystal Growth & Design
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