Radiation damage in a micron-sized protein crystal studied via reciprocal space mapping and Bragg coherent diffractive imaging
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Coughlan, H. D.↗
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Results for “crystallization”
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Photocurrent response of B{sub 12}As{sub 2} crystals to blue light, and its temperature- dependent electrical characterizations
With the global shortage of {sup 3}He gas, researchers worldwide are looking for alternative materials for detecting neutrons. Among the candidate materials, semiconductors are attractive because of their light weight and ease in handling. Currently, we are looking into the suitability of boron arsenide (B{sub 12}As{sub 2}) for this specific application. As the first step in evaluating the material qualitatively, the photo-response of B{sub 12}As{sub 2} bulk crystals to light with different wavelengths was examined. The crystals showed photocurrent response to a band of 407- and 470- nm blue light. The maximum measured photoresponsivity and the photocurrent density at 0.7 V for 470 nm blue light at room temperature were 0.25 A ⋅ W{sup −1} and 2.47 mA ⋅ cm{sup −2}, respectively. In addition to photo current measurements, the electrical properties as a function of temperature (range: 50-320 K) were measured. Reliable data were obtained for the low-temperature I-V characteristics, the temperature dependence of dark current and its density, and the resistivity variations with temperature in B{sub 12}As{sub 2} bulk crystals. The experiments showed an exponential dependence on temperature for the dark current, current density, and resistivity; these three electrical parameters, respectively, had a variation of a few nA to μA, 1-100 μA ⋅ cm{sup −2} and 7.6x10{sup 5}-7.7x10{sup 3} Ω ⋅ cm, for temperature increasing from 50 K to 320 K. The results from this study reported the first photoresponse and demonstrated that B{sub 12}As{sub 2} is a potential candidate for thermal-neutron detectors.
36 MATERIALS SCIENCE↗
Investigation of 2D photonic crystal structure based channel drop filter using quad shaped photonic crystal ring resonator for CWDM system
In this paper, the design & performance of two dimensional (2-D) photonic crystal structure based channel drop filter is investigated using quad shaped photonic crystal ring resonator. In this paper, Photonic Crystal (PhC) based on square lattice periodic arrays of Gallium Indium Phosphide (GaInP) rods in air structure have been investigated using Finite Difference Time Domain (FDTD) method and photonic band gap is being calculated using Plane Wave Expansion (PWE) method. The PhC designs have been optimized for telecommunication wavelength λ= 1571 nm by varying the rods lattice constant. The number of rods in Z and X directions is 21 and 20, with lattice constant 0.540 nm it illustrates that the arrangement of Gallium Indium Phosphide (GaInP) rods in the structure which gives the overall size of the device around 11.4 µm × 10.8 µm. The designed filter gives good dropping efficiency using 3.298, refractive index. The designed structure is useful for CWDM systems. This device may serve as a key component in photonic integrated circuits. The device is ultra compact with the overall size around 123 µm{sup 2}.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
The Crystal Backlighter Imager: A spherically bent crystal imager for radiography on the National Ignition Facility
The Crystal Backlighter Imager (CBI) is a quasi-monochromatic, near-normal incidence, spherically bent crystal imager developed for the National Ignition Facility (NIF), which will allow inertial confinement fusion capsule implosions to be radiographed close to stagnation. This is not possible using the standard pinhole-based area-backlighter configuration, as the self-emission from the capsule hotspot overwhelms the backlighter signal in the final stages of the implosion. The CBI mitigates the broadband self-emission from the capsule hot spot by using the extremely narrow bandwidth inherent to near-normal-incidence Bragg diffraction. Implementing a backlighter system based on near-normal reflection in the NIF chamber presents unique challenges, requiring the CBI to adopt novel engineering and operational strategies. The CBI currently operates with an 11.6 keV backlighter, making it the highest energy radiography diagnostic based on spherically bent crystals to date. For a given velocity, Doppler shift is proportional to the emitted photon energy. At 11.6 keV, the ablation velocity of the backlighter plasma results in a Doppler shift that is significant compared to the bandwidth of the instrument and the width of the atomic line, requiring that the shift be measured to high accuracy and the optics aligned accordingly to compensate. Experiments will be presented that used the CBI itself to measure the backlighter Doppler shift to an accuracy of better than 1 eV. These experiments also measured the spatial resolution of CBI radiographs at 7.0 μm, close to theoretical predictions. Results will be presented from an experiment in which the CBI radiographed a capsule implosion driven by a 1 MJ NIF laser pulse, demonstrating a significant (>100) improvement in the backlighter to self-emission ratio compared to the pinhole-based area-backlighter configuration.
47 OTHER INSTRUMENTATION↗
Modeling dark- and light-induced crystal structures and single-crystal optical absorption spectra of ruthenium-based complexes that undergo SO 2 -linkage photoisomerization
A family of coordination complexes of the type [Ru(SO 2 )(NH 3 ) 4 X] m+ Y n – (m, n = 1 or 2) exhibit optical switching capabilities in their single-crystal states. This striking effect is caused by the light-induced formation of SO 2 -linkage photoisomers, which are metastable if kept at suitably cool temperatures. We modeled the dark- and light-induced states of these large crystalline complexes via plane-wave (PW)- and molecular-orbital (MO)-based density functional theory (DFT) and time-dependent DFT in order to calculate their structural and optical properties; the calculated results are compared with experimental data. We show that the PW-DFT-based periodic models replicate the structural properties of these complexes more effectively than the MO-DFT-based molecular-fragment models, observing only small deviations in key bond lengths relative to the experimentally derived crystal structures. The periodic models were also found to more effectively simulate trends seen in experimental optical absorption spectra, with optical absorbance and coverage of the visible region increasing with the formation of the photoinduced geometries. The contribution of the metastable photoisomeric species more heavily focuses on the lower-energy end of the spectra. Spectra generated from the molecular-fragment models are limited by the geometry of the fragment used and the number of excited-state roots considered in those calculations. In general, periodic models outperform the molecular-fragment models owing to their ability to better appreciate the periodic phenomena that are present in these crystalline materials as opposed to MO approaches, which are finite methods. We thus demonstrate that PW-DFT-based periodic models should be considered as a more than viable method for simulating the optical and electronic properties of these single-crystal optical switches.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Using support vector machines to improve elemental ion identification in macromolecular crystal structures
A method to automatically identify possible elemental ions in X-ray crystal structures has been extended to use support vector machine (SVM) classifiers trained on selected structures in the PDB, with significantly improved sensitivity over manually encoded heuristics. In the process of macromolecular model building, crystallographers must examine electron density for isolated atoms and differentiate sites containing structured solvent molecules from those containing elemental ions. This task requires specific knowledge of metal-binding chemistry and scattering properties and is prone to error. A method has previously been described to identify ions based on manually chosen criteria for a number of elements. Here, the use of support vector machines (SVMs) to automatically classify isolated atoms as either solvent or one of various ions is described. Two data sets of protein crystal structures, one containing manually curated structures deposited with anomalous diffraction data and another with automatically filtered, high-resolution structures, were constructed. On the manually curated data set, an SVM classifier was able to distinguish calcium from manganese, zinc, iron and nickel, as well as all five of these ions from water molecules, with a high degree of accuracy. Additionally, SVMs trained on the automatically curated set of high-resolution structures were able to successfully classify most common elemental ions in an independent validation test set. This method is readily extensible to other elemental ions and can also be used in conjunction with previous methods based on a priori expectations of the chemical environment and X-ray scattering.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Liquid Crystal Orientation and Shape Optimization for the Active Response of Liquid Crystal Elastomers
Liquid crystal elastomers (LCEs) are responsive materials that can undergo large reversible deformations upon exposure to external stimuli, such as electrical and thermal fields. Controlling the alignment of their liquid crystals mesogens to achieve desired shape changes unlocks a new design paradigm that is unavailable when using traditional materials. While experimental measurements can provide valuable insights into their behavior, computational analysis is essential to exploit their full potential. Accurate simulation is not, however, the end goal; rather, it is the means to achieve their optimal design. Such design optimization problems are best solved with algorithms that require gradients, i.e., sensitivities, of the cost and constraint functions with respect to the design parameters, to efficiently traverse the design space. In this work, a nonlinear LCE model and adjoint sensitivity analysis are implemented in a scalable and flexible finite element-based open source framework and integrated into a gradient-based design optimization tool. To display the versatility of the computational framework, LCE design problems that optimize both the material, i.e., liquid crystal orientation, and structural shape to reach a target actuated shapes or maximize energy absorption are solved. Multiple parameterizations, customized to address fabrication limitations, are investigated in both 2D and 3D. The case studies are followed by a discussion on the simulation and design optimization hurdles, as well as potential avenues for improving the robustness of similar computational frameworks for applications of interest.
42 ENGINEERING↗
Comparison of dislocation density tensor fields derived from discrete dislocation dynamics & crystal plasticity simulations of torsion.
Abstract not provided.
Jones, Reese E.↗
Evaluation of a Thermodynamic Ice Crystal Accretion Model using Experimental Data from NASA’s 2nd Fundamental Ice Crystal Icing Test
A thermodynamic model describing ice crystal icing is evaluated using experimental data collected at NASA Propulsion Systems Laboratory. The model makes the distinction between ice accretions that are "freeze-dominated" and "melt-dominated". Freeze-dominated icing occurs when partially melted ice crystals impact a surface and freeze. This type of icing is characterized by strong adhesion. This contrasts with melt-dominated icing, where un-melted ice crystals adhere to a surface. This type of icing is characterized by weak adhesion. In this paper, the thermodynamic model is used to analyze the ice growth rates and facility conditions to explain possible phenomena such as mass loss as well as the melting and freezing fractions. Previous analyses assumed a collection efficiency of unity at the leading edge of the experimental model. LEWICE is used to determine a better estimate of the collection efficiency at the model leading edge as ice accretion grows in time. The result shows that the sticking efficiency could change in a greater percent with time than previously reported.
Ice Crystal Icing↗
Synthesis, crystal structure, and magnetism of A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb)
Ternary intermetallics, A{sub 2}Co{sub 12}As{sub 7} (A=Ca, Y, Ce–Yb), have been synthesized by annealing mixtures of elements in molten Bi at 1223 K. The materials obtained crystallize in the P6{sub 3}/m variant of the Zr{sub 2}Fe{sub 12}P{sub 7} structure type. The unit cell volume shows a monotonic decrease with the increasing atomic number of the rare-earth metal, with the exception of Ce-, Eu-, and Yb-containing compounds. An examination of these outliers with X-ray absorption near edge structures (XANES) spectroscopy revealed mixed valence of Ce, Eu, and Yb, with the average oxidation states of +3.20(1), +2.47(5), and +2.91(1), respectively, at room temperature. Magnetic behavior of A{sub 2}Co{sub 12}As{sub 7} is generally characterized by ferromagnetic ordering of Co 3d moments at 100–140 K, followed by low-temperature ordering of rare-earth 4f moments. The 3d-4f magnetic coupling changes from antiferromagnetic for A=Pr–Sm to ferromagnetic for A=Ce and Eu–Yb. Polarized neutron scattering experiments were performed to support the postulated ferro- and ferrimagnetic ground states for Ce{sub 2}Co{sub 12}As{sub 7} and Nd{sub 2}Co{sub 12}As{sub 7}, respectively. - Graphical abstract: Title arsenides were synthesized by Bi‐flux method. They exhibit mixed valence for A = Ce, Eu, Yb, ferrimagnetism for A = Ca, Y, Pr–Sm, and ferromagnetism for A = Eu–Tm. - Highlights: • A2Co12As7 (A=Ca, Y, Ce–Yb) were synthesized in Bi flux. • Ce, Eu, Yb exhibit mixed valence in the corresponding structures. • The character of 3d‐4f magnetic coupling changes at the half‐filled f shell. • Materials behave as ferrimagnets for A=Ca, Y, Pr–Sm and as ferromagnets for A=Eu–Yb.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Precursor routes to quaternary intermetallics: Synthesis, crystal structure, and physical properties of clathrate-II Cs{sub 8}Na{sub 16}Al{sub 24}Si{sub 112}
A new quaternary clathrate–II composition, Cs{sub 8}Na{sub 16}Al{sub 24}Si{sub 112}, was synthesized by kinetically controlled thermal decomposition (KCTD) employing both NaSi and NaAlSi as the precursors and CsCl as a reactive flux. The crystal structure and composition of Cs{sub 8}Na{sub 16}Al{sub 24}Si{sub 112} were investigated using both Rietveld refinement and elemental analysis, and the temperature dependent transport properties were investigated. Our results indicate that KCTD with multiple precursors is an effective method for the synthesis of multinary inorganic phases that are not easily accessible by traditional solid-state synthesis or crystal growth techniques. - Graphical abstract: Quaternary Cs{sub 8}Na{sub 16}Al{sub 24}S{sub 112} clathrate–II was synthesized for the first time by kinetically controlled thermal decomposition (KCTD) employing a NaSi+NaAlSi precursor mixture with CsCl as the reactive flux, and the structural and transport properties were investigated. Our approach demonstrates a new synthetic pathway for the synthesis of multinary inorganic compounds. This work reports the exploration of a new clathrate composition as this class of materials continues to be of interest for thermoelectrics and other energy-related applications.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
The crystal structure of Fe2S at 90 GPa based on single-crystal X-ray diffraction techniques
The Fe-S system was explored in a laser-heated diamond-anvil cell at 89(2) GPa and 2380(120) K to better understand the phase stability of Fe 2 S. Upon temperature quenching, crystallites of Fe 2 S were identified, and their structure was investigated using single-crystal X-ray diffraction techniques. At these conditions, Fe 2 S adopts the C23 structure (anti-PbCl 2 , Co 2 P) with space group Pnma (Z = 4). This structure consists of columns of corner-sharing, FeS 4 tetrahedra, and columns of edge-sharing FeS 5 square pyramids linked along edges in the b direction. Sulfur is in ninefold coordination with Fe. This work marks the first high-pressure structural solution and refinement of Fe 2 S synthesized in a multigrain Fe+FeS sample at 90 GPa and 2400 K and establishes the stability of C23 Fe 2 S at these conditions. A previous powder diffraction study reports an orthorhombic Fe 2 S phase with a C37, Co 2 Si-like unit cell above 190 GPa. A C23–C37 structural transition is inferred to explain the previously observed unit-cell parameters at higher pressures and temperatures. These results highlight the utility of applying single-crystal X-ray diffraction techniques to high P-T multigrain samples to explore the structural properties of iron-rich phases in Earth and planetary cores.
36 MATERIALS SCIENCE↗
An Atomic View of Cation Diffusion Pathways from Single;#8208;Crystal Topochemical Transformations
Abstract not provided
Handy, Joseph V.↗
A Literal Elytral Rainbow: Tunable Structural Colors Using Single Diamond Biophotonic Crystals in Pachyrrhynchus congestus Weevils
Abstract not provided
Wilts, Bodo D.↗
Synthesis, Crystal and Electronic Structure of Layered AM Sb Compounds ( A = Rb, Cs; M = Zn, Cd): Synthesis, Crystal and Electronic Structure of Layered AM Sb Compounds ( A = Rb, Cs; M = Zn, Cd)
Synthesis, crystal structure, thermal stability, and electronic band structure of four new metal antimonides AMSb (A = Rb, Cs; M = Zn, Cd) are reported. CsZnSb and RbZnSb crystallize in the hexagonal ZrBeSi structure type, in a P6 3 /mmc space group (no. 194, Z = 2) and unit cell dimensions of a = 4.5588(2)/4.5466(4) Å and c = 11.9246(6)/11.0999(10) Å. CsCdSb and RbCdSb crystallize in the tetragonal PbFCl structure type in a P4/nmm space group (no. 129; Z = 2) and unit cell parameters of a = 4.8884(5)/4.8227(3) Å and c = 8.8897(9)/8.5492(7) Å. All four compounds are air- and water-sensitive and are shown through DSC measurements to decompose between 975 K and 1060 K. Analysis of the calculated electronic band structure shows that the Zn-containing antimonides are topologically trivial narrow bandgap semiconductors, whereas Cd-containing compounds exhibit a band inversion along Γ-Z direction.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Hemoglobin crystals immersed in liquid oxygen reveal diffusion channels
Highlights: • Crystal structure of Human Hemoglobin were solved after immersion in liquid oxygen. • Immersion in liquid oxygen oxidizes the heme-center revealing aquomethemoglobin. • Immersion in liquid oxygen also reveals the footprints of oxygen channels. • These channels contain medically relevant mutations that modulate oxygen affinity. Human hemoglobin (HbA) transports molecular oxygen (O{sub 2}) from the lung to tissues where the partial pressure of O{sub 2} is lower. O{sub 2} binds to HbA at the heme cofactor and is stabilized by a distal histidine (HisE7). HisE7 has been observed to occupy opened and closed conformations, and is postulated to act as a gate controlling the binding/release of O{sub 2}. However, it has been suggested that HbA also contains intraprotein oxygen channels for entrances/exits far from the heme. In this study, we developed a novel method of crystal immersion in liquid oxygen prior to X-ray data collection. In the crystals immersed in liquid oxygen, the heme center was oxidized to generate aquomethemoglobin. Increases of structural flexibility were also observed in regions that are synonymous with previously postulated oxygen channels. These regions also correspond to medically relevant mutations which affect O{sub 2} affinity. The way HbA utilizes these O{sub 2} channels could have a profound impact on understanding the relationship of HbA O{sub 2} transport within these disease conditions. Finally, the liquid oxygen immersion technique can be utilized as a new tool to crystallographically examine proteins and protein complexes which utilize O{sub 2} for enzyme catalysis or transport.
60 APPLIED LIFE SCIENCES↗