Poster Session II

Conference: 2020: 70th ACA Annual Meeting
08/03/2020: 4:00 PM  - 5:00 PM 
PS2 
Poster Session 
Virtual  

Description

The ACA holds three evening poster sessions. Poster sessions are organized by the Poster Chairs and feature presentations covering a range of crystallography topics. Poster presentations may not seem as prominent as oral presentations, but they offer a terrific opportunity to interact with other scientists in your field in a structured way.

Presentations

Photocrystallographic studies of novel nickel (II) nitro complex supplemented by IR spectroscopy and multi-temperature XRD experiments

The importance of transition-metal switchable compounds of real-life applications is rapidly increasing, thus investigations of nickel (II) organic complexes in which metal centre is coordinated by molecular fragments that can exist in multiple isomeric forms (e.g. NO2, SO2 , N2) cannot be overestimated. Hence, the current study was devoted to obtain novel promising photoswitchable materials characterized by desired reversibility, high conversion percentage and stability. The designed model compound is shown in Figure 1. As can be seen, the nickel(II) centre is coordinated by the ambidentate nitro ligand and the (N,N,O)-donor moiety. For the purpose of thorough analysis of its photoswitchable properties and the isomerisation reaction features, IR spectroscopy, multi-temperature and photocrystallographic XRD experiments were conducted and supported by computational investigations. Optimal photoisomerisation conditions were determined on the basis of multi-temperature XRD and spectroscopic experiments. The studied complex crystallises in the P-1 space group with one molecule in the asymmetric unit. Upon visible light irradiation the nitro isomer transforms to the endo-nitrito form reaching about 25% conversion in the form of a single crystal sample and 100% as a powder according to the IR spectroscopy results. The generated metastable state species exist up to 200 K. Intermolecular contacts, linkage isomers' relative stability, reaction cavity volumes and crystal packing were thoroughly investigated to understand the nitro-nitrito linkage isomerisation mechanism. [1] Kamiński, R, Jarzembska, K. N., Kutyła, S. E. & Kamiński, M. (2016). J.Appl.Cryst.. 49, 1383. [2] Hatcher, L. E., Skelton, J. M., Warren, M. R. & Raithby, P. R. (2019). Acc. Chem. Res. 52, 4, 1079. Keywords: photocrystallography; nickel (II) nitro complexes; photoswitchable compounds The authors thank the PRELUDIUM grant (2017/25/N/ST4/02440) of the National Science Centre in Poland and the Inter-Faculty of Individual Studies in Mathematics and Natural Sciences, University of Warsaw, for financial support. The Wrocław Centre for Networking and Supercomputing (grant No. 285) is gratefully acknowledged for providing computational facilities. The in-house X-ray diffraction experiments were carried out at the Department of Physics, University of Warsaw, on Rigaku Oxford Diffraction SuperNova diffractometer, which was co-financed by the European Union within the European Regional Development Fund (POIG.02.01.00-14.122/09) 

View Proposal 277

Author

Patryk Borowski, University of Warsaw Warsaw

Additional Author(s)

Sylwia E. Kutniewska, University of Warsaw Warsaw
Radosław Kamiński, University of Warsaw Warsaw
Katarzyna N. Jarzembska, University of Warsaw Warsaw

Controlling π-Stacking Interactions in a Series of Novel Heteroacene Derivatives

The understanding and control of intermolecular forces allows for the creation of supramolecular architectures held together by relatively weak, flexible interactions. The exploitation of π-π stacking interactions can produce materials with dynamic properties such as crystal to crystal transitions.[1] Co-facial π-interactions are also important in the preparation of semiconducting organic materials,[2] however, face-to-face π-stacking is generally repulsive and often disfavoured.[3] In our development of an SNAr-based methodology for the synthesis of heteropentacene analogues 1a-c we synthesised a series of electronically biased 1,2,3,4-tetrasubstituted dibenzodioxin (2a-c) and phenoxazine (3a-c) derivatives.[4] An examination of the crystal structures of 2a-c and 3a-c indicates that a combination of electronic bias and C−H substitution affords compounds which tend to π-stack in a co-facial, antiparallel manner. A search of the Cambridge Structural database for representative structures was also conducted. The results indicate such motifs could be valuable building blocks for supramolecular design of materials held together by co-facial π-π stacking interactions. References: [1] Reger, D. L.; Horger, J. J.; Smith, M. D.; Long, G. J.; Grandjean, F. Inorg. Chem. 2011, 50 (2), 686–704. [2] Anthony, J. E. Angew. Chem. Int. Ed. 2008, 47 (3), 452–483. [3] Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112 (14), 5525–5534. [4] Hiscock, L. K.; Raycraft, B. M.; Wałęsa-Chorab, M.; Cambe, C.; Malinge, A.; Skene, W. G.; Taing, H.; Eichhorn, S. H.; Dawe, L. N.; Maly, K. E. Chem. Eur. J. 2019, 25 (4), 1018–1028. 

View Proposal 240

Author

Lana Hiscock, Wilfrid Laurier University Waterloo, ON 

Additional Author

Louise Dawe, Wilfrid Laurier Univ Kitchener, ON 

Structural Studies of Manganese(III) Complex with Spin-Crossover and Thermochromic Properties

The phenomenon of spin-crossover (SCO) has been of great interest due to the bistability of the materials and the search for new technologies and applications. The transition implies a reversible change from high to low spin or vice versa[1]. This magnetic behavior can be induced by external disturbances, such as, temperature, pressure and/or light (LIESST) in 3d4 to 3d7 configurations. More rare and exceptional are the cases in Cr(II) and Mn(III)[2,3]. A new SCO manganese(III) complex with the formula [MnIII(5-MeO-sal-N-1-5-8-12)]Cl has been studied by X-ray diffraction, using the octahedral deviation parameters[4] Σ/° (12 angles of 90°) and trigonal distortion θ/° (24 angles of 60°), that allow the classification of spin states. The crystallographic study was carried out at four different temperatures (100 K, 290 K, 350 K and 400 K) and the unit cell was analyzed at twelve different temperatures in a range of 90 K to 400 K, finding large changes in the coordination sphere. At 400 K octahedral deviations parameters were obtained according to high spin (HS) with 59.2(4)° and 149.5(7)°, and at 100 K the values are typical of low spin (LS) with 34.0(4)° and 79.8(6)°, for Σ/° and θ/°, respectively. The magnetic susceptibility confirms a gradual transition with a T1/2 of 281K, according to the large changes of the unit cell between 250 K and 310 K (figure 1). The definitive evidence of the electronic transition corresponds to the thermochromism in solid state. On cooling to below 250 K, the color begins to visually change and by 90 K the single crystal has turned red (figure 2) with all the electronic population in LS state (3T1g ground state). Finally, a comparison with the MnIII analogous complexes was made using the octahedral distortion parameters obtaining a trend and dispersion diagram of the reported values. Figure 1. β angle (red triangles) and volume (black dots) Figure 2: Thermochromism at 100 K and 400 K variation by temperature References [1] P. Gütlich, A.B. Gaspar, Y. Garcia, Beilstein J. Org. Chem. 9 (2013) 342–391. [2] S. Wang, W.-T. Xu, W.-R. He, S. Takaishi, Y.-H. Li, M. Yamashita, W. Huang, Dalt. Trans. 45 (2016) 5676–5688. [3] S. Wang, Y.J. Li, F.F. Ju, W.T. Xu, K. Kagesawa, Y.H. Li, M. Yamashita, W. Huang, Dalt. Trans. 46 (2017) 11063–11077. [4] R. Pritchard, S.A. Barrett, C.A. Kilner, M.A. Halcrow, T, J. Chem. Soc. Dalt. Trans. (2008) 3159–3168. Keywords: Spin-Crossover; Thermochromism. Acknowledgements to the Fondecyt Project No. 1130640, Fondequip EQM120095 (Single-CrystalXRD). David Villaman thanks Conicyt Scholarship Nº 21151093, PUCV Internship Scholarship and Newcastle University for the support. 

View Proposal 409

Author

David Villaman

Additional Author(s)

Charles McMonagle, Newcastle University
Michael Probert, Newcastle University
Octavio Peña, Université de Rennes-1, Rennes
Yanko Peña, Universidad Santo Tomás
Mauricio Fuentealba, Pontificia Universidad Católica de Valparaíso Valparaíso, Valparaíso 

Structural study by X-ray diffraction of iron (III) complexes

The compounds with Spin-crossover (SCO) phenomenon have a reversible exchange between a low spin (LS) state that is stable at low temperatures and a high spin (HS) state that is stable at high temperatures. In general, the reversible process in solid systems is controlled by intermolecular cooperatives interactions [1]. The correlation between the structures with the physical properties is crucial for the interaction's identification and the understanding of the complex processes that control the phenomenon SCO. Most of the materials SCO studied are complexes with 3d4 – 3d7 metals with coordination sphere N2O4 [1-2]. Structural studies were performed comparing the structures of a series of complexes informed in this work and previously described by our research group [2] to establish relationships with magnetic properties [3]. This work aims to carry out a structural study of complexes with coordination sphere N4O2, for which purpose iron (III) complexes have synthesized from FeBr2 and FeCl3 salts with hexadentate and tridentate ligands forming octahedral systems. These complexes have been characterized by FT-IR, UV-vis spectroscopy and single-crystal X-ray diffraction. Using the crystallographic data is possible to determine, in octahedral complexes, the distortion of the coordination sphere during the spin transition determining the distortion parameters. For instance, in the complex [C1] Br, the distances between Fe atom to atoms in the coordination sphere were similar in the range of 170 K to 298 K, wherefore the octahedral parameters not undergo a significant change (∑º/ 79.5 a 170 K y 80.1 a 298 K y Θº/ 226.1 a 170 K y 229.1 a 298 K). These parameters indicate that in that temperature range, this complex is in High Spin State. [1] D.J. Harding, P. Harding, W. Phonsri, Spin crossover in iron (III) complexes, Coord. Chem. Rev. 313 (2016) 38–61. [2] K. S. Kumar, Y. Bayeh, T. Gebretsadik, F. Elemo, M. Gebrezgiabher, M. Thomas, M. Ruben. Spin-crossover in iron(II)-Schiff base complexes, Dalton Trans., 2019,48, 15321-15337 [3] V. Artigas, Estudios estructurales a través de Difracción de Rayos-X en complejos de hierro (III) con esfera de coordinación FeN4O2 con potenciales propiedades spin-crossover, Pontificia Universidad Católica de Valparaíso, 2018. [4] P. Guionneau, Crystallography and spin-crossover. A view of breathing materials, Dalt. Trans. 43 (2014) 382–393. Keywords: Spin-Crossover; iron (III) complexes; spin transition. 

View Proposal 408

Author

Nicole Nilo

Additional Author

Mauricio Fuentealba, Pontificia Universidad Católica de Valparaíso Valparaíso, Valparaíso 

Synthetic investigation on structure-property relationships in the Ca2-xMnxTi2O6 quadruple perovskite system

Pressure assisted synthesis is a proven route for expanding the explorable range of phase space in order to discover and stabilize new metastable ABO[sub]...[/sub]3 perovskite-type structures. Recently, a new class of complex perovskites termed quadruple perovskites (QPv) have been investigated for their unusual cation ordering and interesting ferroic properties [1]. One intriguing member of this family is CaMnTi[sub]...[/sub]2O[sub]...[/sub]6, which displays ferroelectric character (T[sub]...[/sub]C = 630K) and was previously reported by High-Pressure High-Temperature (HP-HT) synthesis methods at 1200°C -1700 °C and 7 GPa [2]. A recent work [3] showed that related Ca-rich compositions in the Ca[sub]...[/sub](2-x)Mn[sub]...[/sub]xTi[sub]...[/sub]2O[sub]...[/sub]6 series could be achieved at much lower pressures (100 MPa) using a Spark Plasma Sintering (SPS) approach. Our present study explores the optimized P-T synthesis conditions for compositions across the Ca[sub]...[/sub](2-x)Mn[sub]...[/sub]xTi[sub]...[/sub]2O[sub]...[/sub]6 series under a variety of different synthetic techniques (HP-HT, SPS, etc.). Furthermore, the effect of varying synthetic parameters (Ca/Mn ratio, pressure, temperature, SPS current, etc.) on competing phase stabilities, structural distortions, and cation ordering in Ca[sub]...[/sub](2-x)Mn[sub]...[/sub]xTi[sub]...[/sub]2O[sub]...[/sub]6 series of QPv is discussed. Finally, connections are proposed concerning the structure-property relationship, in particular for the ferroelectric transition temperature (T[sub]...[/sub]C) and dielectric permittivity response. 

View Proposal 376

Author

Subhransu Bhoi, Institut de Chimie de la Matière Condensée de Bordeaux PESSAC

Additional Author(s)

Murielle LEGENDRE, Institut Néel, UPR 2940, 38042 Grenoble FRANCE Grenoble
Céline GOUJON, Institut Néel, UPR 2940, 38042 Grenoble FRANCE Grenoble
Michael JOSSE, University of Bordeaux, ICMCB, UMR 5026, 33600 Pessac, FRANCE Pessac
Matthew SUCHOMEL, ICMCB-CNRS UMR 5026, 33600 Pessac FRANCE Pessac

Bis(S-(-)-1-phenylethylammonium) tetrabromidocuprate(II): another step in the sequential breakdown of the A2CuX4 layer perovskite structure

The A2CuX4 layer perovskite structure is well represented in halidocuprates in which monopositive A cations form bilayers with ammonium head groups directed outward into interleaving layers of corner-sharing Cu(X4/2)X2 octahedra (X = Cl or Br).  In these structures the A cations typically are protonated primary amines or anilines that have a narrow enough cross section to pack together in a bilayer without disrupting the 2-D inorganic structure.  Our laboratory has previously reported (Bond & Nalla ACA Annual Meeting (2013) abstract T-52) the structures of bis(4-chloro-2,6-dimethylanilinium)- and bis((R,S)-1-phenylethylammonium)-tetrachloridocuprate(II) in which the bulkier A cations now force the 2-D inorganic structure to break apart into 1-D chains or 0-D complexes, respectively, while still maintaining the organic bilayer.  The title structure consists of 0-D CuBr42- complexes that, by virtue of their larger size, force the organic bilayer to spread out and lead to its partial collapse.  In contrast to both the racemic and enantiomeric bis(1-phenylethylammonium structures (the latter of which is also presented) which both crystallize in polar space groups (orthorhombic Aea2 and monoclinic C2, respectively) with one symmetrically unique organic cation, the title structure crystallizes in orthorhombic P212121 with two symmetrically inequivalent organic cations.  The sequential breakdown of the aristotype K2NIF4 2-D structure (I4/mmm) to these 1- and 0-D structures is followed through descent of symmetry. 

View Proposal 389

Author

Madison Christian, Southeast Missouri State University Cape Girardeau, MO 

Additional Author

Marcus Bond, Dept of Chemistry and Physics, Southeast Missouri State University Cape Girardeau, MO 

Using crystallographic models to experimentally measure partial atomic charges with comparison to quantum calculations

Modern crystallographic refinement methods treat each atom in a molecule as neutral with spherical electron density. Atoms, however, exhibit partial atomic charges arising from intramolecular forces via bonding. These partial charges are crucial for understanding electronic structure and bulk physical properties of molecules. Typically the polarity and polarizability of molecules are calculated using IR and Raman spectroscopy, respectively. While these techniques can be used on small molecules, fine elucidation of partial charges on individual atoms is still unrealized. Here we present crystallographic refinement developments that allow us to refine electron density around individual atoms to experimentally calculate partial atomic charges. Comparison between these experimentally calculated charges to theoretical quantum calculated charges will also be presented. 

View Proposal 410

Author

Taylor Keller, Temple University Philadelphia, PA 

Additional Author(s)

Michael Zdilla, Chemistry, Temple Univ Philadelphia, PA 
Prabhat Prakash, Temple University Philadelphia, PA 
Alex Byrne, Temple University Philadelphia, PA 

Structural study of phenylperimidines with potential applications as corrosion inhibitors

Worldwide the protection against the corrosion is mainly based on the use of corrosion inhibitors; they exist in a variety of organic and inorganic compounds added on the metal surface. An inhibitor must possess structural features, such as having a planar geometry, π-conjugated system, bearing functional groups and heteroatoms with unshared electron pairs. With these characteristics, corrosion inhibitors will generate a barrier against corrosion through physisorption and chemisorption processes. In this work, we carried out the syntheses and characterization, using vibrational spectroscopy, of phenylperimidines compounds synthesized from 1,8-diaminonaphtalene and 2-hydroxybenzaldehyde. The condensation reaction is carried out by refluxing the reactants in toluene obtaining the 2-(1H-perimidin-2-yl) phenol (a) compound and, in toluene/methanol 2: 1 mixture, the 2-(2,3-Dihydro -1H-perimidin-2-yl) -phenol (b) is formed (Fig. 1). The crystal structures of both compounds (a) and (b) has been determined by X-ray single-crystal diffraction. From the molecular and crystalline structures, it is observed that the structure of (a) only crystallizes with one molecule in the asymmetric unit forming an intramolecular hydrogen bond O1-H1···N1 granting planarity to the system. On the other hand, the compound (b) crystallizes with two formula units in the asymmetric unit. In this case, an intramolecular hydrogen bond is formed between the O1-H1···N1 and the O1A-H1A···N2A atoms. Both compounds are postulated as potential corrosion inhibitors, since the crystalline and molecular structures of (a) and (b) present intra- and intermolecular hydrogen bonds, have functional groups bearing heteroatoms and contain a π-conjugated system in (a) that yields to a flat geometry with high electronic communication unlike (b) that loses planarity over C11 with sp3 hybridization. The cyclic voltamperometry measurement of (a) is reported (Fig. 2). The oxidation process is observed with a potential peak defined in +0.328V and the reduction processes with two waves at + 0.106V and –0.346V. Also, there are no drastic changes in the different cycles of voltammetry, indicating the structural stability of the compounds. Therefore, these compounds could be used as a corrosion inhibitor by the conjugation of aromatic rings capable of interacting with the metal surface in a specific medium and metal or alloy for study and simulation. 

View Proposal 405

Author

Elizabeth Olave Negrete, Pontificia Universidad Católica de Valparaíso Valparaíso

Additional Author(s)

Maria Isidora Espinoza, Pontificia Universidad Católica de Valparaíso Valparaíso, Valparaíso 
Vania Artigas, Pontificia Universidad Católica de Valparaíso Valparaíso, Valparaíso 
Rodrigo Sánchez, Pontificia Universidad Católica de Valparaíso Valparaíso, Valparaíso 
Rosa Vera, Pontificia Universidad Católica de Valparaíso Valparaíso, Valparaíso 
Mauricio Fuentealba, Pontificia Universidad Católica de Valparaíso Valparaíso, Valparaíso 
Juliet Aristizabal, Universidad Técnica Federico Santa María Valparaíso, Valparaíso 

Direct and Simple Experimental Crystallographic Method to Calculate Partial Charges with Atomistic Correspondence to ab-initio Methods

Derivation of partial charges in small and large scale molecular systems is important for modeling of various experimental and theoretical properties like dipole moments, auto-correlation functions, charge disparity, understanding of dispersion, benchmark of classical MD simulations and electrostatic potential energy surface mapping. A correspondence between theoretical calculations (based on single/small number of molecules) is usually established with macroscopic IR/Raman spectra or dipole moment measurements. Such comparisons are indirect and lack a fine mapping of electrostatic potential from theory to experiment. In a new approach developed as the experimental part of this work, partial charges are calculated from crystallographic model refinement. The experimental method exhibits a satisfactory correspondence with partial charges obtained using quantum chemistry calculations. Particularly, gas phase partial charges from CHELPG method and condensed phase Lowdin charges correlate well and validate this experimental method. 

View Proposal 411

Author

Prabhat Prakash, Temple University Philadelphia, PA 

Additional Author(s)

Alex Byrne, Temple University Philadelphia, PA 
Taylor Keller, Temple University Philadelphia, PA 
Michael Zdilla, Chemistry, Temple Univ Philadelphia, PA 

1,2-Cyclobutanecarboxylates Synthesized Using Photoreaction and Esterification

Esters are importance targets or intermediates in the synthesis of plasticizers, perfumes, flavor chemicals, cosmetics, fine chemicals, pharmaceuticals, and chiral auxiliaries. However, ophthalates, a group of 1,2-benzenedicarboxylates derived from petrochemicals, are being gradually replaced by phthalate-free plasticizers in many products due to health concerns. Truxinates, a family of 1,2-cyclobutanecarboxylates found in many natural products, share the structural similarities with o-phthalates and may serve as nontoxic phthalate alternatives. In this poster presentation, we report the synthesis of a series of mono- and di-esters of a 1,2-cyclobutanecarboxylic acid (CBDA-4, Figure 1) from trans-cinnamic acid using [2+2] photocycloaddition and subsequent esterification. The structures of many 1,2-cyclobutanecarboxylates were successfully determined by single crystal X-ray diffraction. These esters show promising potential for use in wide-ranging applications. For example, the cyclobutane ring in some esters was thermally cleavable at high temperature, providing a method by which materials made from them could be easily recyclable. References [1] Amjaour. H, Z. Wang, Mabin. M and Q. R. Chu, Chem. Commun. 2019, 55, 214-217. [2] Wang, Z.; Scheuring, M.; Mabin, M.; Shahni, R.; Wang, Z. D.; Ugrinov, A.; Butz, J.; Chu, Q. R., ACS Sustainable Chem. Eng. 2020, 8, 8909-8917. [3] B. Cornils and P. Lappe, "Dicarboxylic Acids, Aliphatic" in Ullmann's encyclopedia of industrial chemistry, Wiley-VCH, Weinheim, 2014. 

View Proposal 401

Author

Houssein Amjaour, University of North Dakota Grand forks, ND 

Additional Author(s)

Zhihan Wang, PhD Grand Forks, ND 
Micah Mabin, Student Grand Forks, ND 
Qianli R. Chu, advisor Grand Forks, ND 

Bimetallic platinum-based complexes: syntheses and synchrotron X-ray radiation structural studies

Today, the bimetallic palladium-based carboxylic complexes shown high reactivity in homogeneous catalytic hydrogenation processes of unsaturated hydrocarbons, and their effectiveness as precursors of supported heterogeneous bimetallic catalysts with improved activity and selectivity. Until recently, convenient single-molecular precursors of the supported catalysts, platinum-based carboxylates were not available because of inaccessibility and low reactivity of the starting material platinum acetate [Pt[sub]4[/sub](OOCMe)[sub]8[/sub]]. In this work, we synthesized more than 20 novel homo- and heterometallic acetate complexes of platinum and some their derivatives with N-donor ligands. Two synthetic approaches were developed based on the platinum acetate blue (PAB, Pt(OOCMe)[sub]2.25-2.75[/sub]) [1] and potassium hexahydroxyplatinate K[sub]2[/sub][Pt(OH)[sub]6[/sub]] [2,3] as starting materials. The structures of the complexes were esrablished by conventional single-crystal X-ray diffraction technique and with using synchrotron radiation single crystal XRD methods. («Belok» beamline of the specialized source of synchrotron radiation "KISI-Kurchatov", National Research Center «Kurchatov Institute», Moscow, Russian Federation) [4]. Acknowledgments: This work is supported by the Russian Science Foundation under grant 18-73-10206. This research was performed using the equipment of the JRC PMR IGIC RAS. References: [1] N.V. Cherkashina, D.I. Kochubey, V.V. Kanazhevskiy, V.I. Zaikovskii, V.K. Ivanov, A.A. Markov, A P. Klyagina, Zh.V. Dobrokhotova, N.Y. Kozitsyna, I.B. Baranovsky, O.G. Ellert, N.N. Efimov, S.E. Nefedov, V.M. Novotortsev, M.N. Vargaftik, I.I. Moiseev. // Inorganic Chemistry, V. 53 (2014), 8397–8406. [2] Ilya A. Yakushev, Igor P. Stolarov, Natalia V. Cherkashina, Andrei V. Churakov, Yan V. Zubavichus, Alexander A. Markov, Alexander E. Gekhman, Michael N. Vargaftik. // Inorganica Chimica Acta, V. 508 (2020), 119631. [3] I.P. Stolarov, N.V. Cherkashina, I.A. Yakushev, A.V. Churakov, A.B. Kornev, E.V. Fatyushina. // Russian Journal of Inorganic Chemistry, V. 65 (2020), 4, 507-513 [4] Roman D. Svetogorov, Pavel V. Dorovatovskii, Vladimir A. Lazarenko. Belok/XSA diffraction beamline for studying crystalline samples at Kurchatov Synchrotron Radiation Source // Crystal Research and Technologies, V. 55 (2020), 5, 1900184 

View Proposal 388

Author

Ilya Yakushev, Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences Moscow

Additional Author(s)

Igor Stolarov, Kurnakov Institute of general and inorganic chemistry (RAS) Moscow
Michael Vargaftik, Kurnakov Institute of general and inorganic chemistry (RAS) Moscow

Upconversion Enhancement via Functionalization of Plasmonic Nanoparticles

Recently, many techniques have been explored to increase the efficiency of triplet-triplet annihilation upconversion (TTAUC) materials by locking the sensitizers and acceptors into fixed locations. Previous work has shown that isolating the position of the sensitizer onto a gold nanoparticle can increase the efficiency of the TTAUC process. This increase is believed to derive from the plasmonic structure of the nanoparticles. Our current direction is to isolate the acceptor on a gold nanoparticle. The location of the acceptor can be tuned and will afford an increase in the efficiency of the TTAUC system. Ultimately, the goal is to increase the efficient harnessing of energy from our sun by utilizing the plasmonic nature of gold nanoparticles. Crystallography is at the heart of the characterization of these novel acceptor compounds. 

View Proposal 390

Author

Nathaniel Barker, University of Cincinnati Cincinnati, OH 

Additional Author(s)

Emily Westbrook, University of Cincinnati Department of Chemistry Cincinnati, OH 
Jeanette Krause, University of Cincinnati Department of Chemistry Cincinnati, OH 
Peng Zhang, University of Cincinnati Department of Chemistry Cincinnati, OH 

Materializing Rival Ground States in the Barlowite Family of Kagome Magnets

Quantum magnets display exotic phases that may be strongly influenced by small differences in structure and composition. The quantum spin liquid (QSL) is an unusual magnetic ground state, characterized by long-range quantum entanglement of the spins but a lack of long-range magnetic order down to T = 0 K.[1] Materials with a kagome arrangement of Cu2+ ions are prime candidates as the QSL ground state is believed to be attainable in highly frustrated spin-1/2 systems. Newly synthesized crystalline barlowite (Cu4(OH)6FBr) and Zn-substituted barlowite demonstrate the delicate interplay between singlet states and spin order on the spin-1/2 kagome lattice.[2] We find that when the bonds of the kagome lattice are modulated with a periodic pattern, new quantum ground states emerge. Comprehensive structural and magnetic measurements (including single crystal and powder X-ray diffraction, powder neutron diffraction, and single crystal neutron scattering) address open questions about their crystal and magnetic structures. We reveal a clear structure-properties relationship between two variants of barlowite with distinct low-temperature structures (orthorhombic Pnma and hexagonal P63/m).[3] This hexagonal variant is novel, and we are able to grow large single crystals. Its phase transition involves a subtle symmetry lowering, and its kagome lattice contains a motif of distorted and undistorted triangles, for which numerical simulations predict a pinwheel valence bond crystal state instead of a QSL state. The presence of interlayer spins eventually leads to novel pinwheel q=0 magnetic order, which we elucidate with single crystal neutron scattering. Sizable single crystals of QSL candidate Zn-substituted barlowite (Cu3.44Zn0.56(OH)6FBr) were grown for the first time and have an intermediate level of Zn substitution compared to Cu3.05Zn0.95(OH)6FBr and herbertsmithite. Site-specific X-ray anomalous dispersion, extended X-ray absorption fine structure, and X-ray absorption spectroscopy measurements demonstrate that Zn2+ occupies a perfect trigonal prismatic interlayer site with minimal amount of antisite defects. They also demonstrate that the interlayer Zn2+ coordination in Zn-substituted barlowite is distinct from that in herbertsmithite. Significantly, no structural transition is observed at low temperature in either composition of Zn-substituted barlowite, and no magnetic transition occurs down to T = 0.1 K, indicating a surprising robustness of the QSL against interlayer Cu2+ impurities. These samples span a spectrum of quantum spin liquidity, allowing this exotic ground state to be probed systematically. References: [1] Norman, M. R. (2016). Rev. Mod. Phys. 88, 041002. [2] Smaha, R. W. et al. (2018). J. Solid State Chem. 268, 123-129. [3] Smaha, R. W. et al. (2020). npj Quantum Materials 5, 23. 

View Proposal 375

Author

Rebecca Smaha, Stanford University Stanford, CA 

Additional Author(s)

Wei He, Stanford University Stanford, CA 
Jack Jiang, Stanford University Stanford, CA 
Charles Titus, Stanford University Stanford, CA 
Jiajia Wen, Stanford University Stanford, CA 
Young Lee, Stanford University Stanford, CA 

An Introduction to the Gold Standard for Macromolecular Crystallography Diffraction Data

In a major step forward for MX data management, a large portion of the research community concerned with High Data-Rate Macromolecular Crystallography (HDRMX) has now agreed to an updated specification of data and metadata for diffraction images produced at synchrotron light sources and X-ray free electron lasers (XFELs) [Herbert J. Bernstein, Andreas Förster, Asmit Bhowmick, Aaron S. Brewster, Sandor Brockhauser, Luca Gelisio, David R. Hall, Filip Leonarski, Valerio Mariani, Gianluca Santoni, Clemens Vonrhein, Graeme Winter, "Gold Standard for Macromolecular Crystallography Diffraction Data", IUCrJ submitted 2020]. This talk is an introduction to the new "Gold Standard" with use case examples for synchrotron and XFEL data. "Macromolecular crystallography (MX) is the dominant means of determining the three-dimensional structures of biological macromolecules. Over the last few decades, most MX data have been collected at synchrotron beamlines using a large number of different detectors produced by various manufacturers and taking advantage of various protocols and goniometry. These data came in their own formats, sometimes proprietary, sometimes open. The associated metadata rarely reached the degree of completeness required for data management according to Findability, Accessibility, Interoperability, and Reusability (FAIR) principles. Efforts to reuse old data by other investigators or even by the original investigators some time later were often frustrated. "In the culmination of an effort dating back more than two decades, a large portion of the research community concerned with High Data-Rate Macromolecular Crystallography (HDRMX) has now agreed to an updated specification of data and metadata for diffraction images produced at synchrotron light sources and X-ray free electron lasers (XFELs). This "Gold Standard" will facilitate processing of datasets independent of the facility at which they were collected and enable data archiving according to FAIR principles, with a particular focus on interoperability and reusability. This agreed standard builds on the NeXus/HDF5 NXmx application definition and the International Union of Crystallography (IUCr) imgCIF/CBF dictionary, and it is compatible with major data processing programs and pipelines. Just as with the IUCr CBF/imgCIF standard from which it arose and to which it is tied, the NeXus/HDF5 NXmx Gold Standard application definition is intended to be applicable to all detectors used for crystallography, and all hardware and software developers in the field are encouraged to adopt and contribute to the standard." 

View Proposal 260

Author

Herbert Bernstein, Ronin Institute for Independent Scholarship, c/o NSLS-II, Brookhaven National Lab, Bldg 745 Bellport, NY 

The pymolsnips library to aid the writing of PyMOL scripts

Scripts of PyMOL commands are useful for applying the numerous parameters required to exert exquisite control over the appearance of a molecular model. Unfortunately, the vast majority of PyMOL users have trouble recalling the commands and their syntax in the PyMOL scripting language because they do not use PyMOL everyday. This difficulty with the recall of commands slows the writing of new scripts. Experienced users address this problem by recycling their old script files, but this option does not work well when embarking on a new task for which a similar script cannot be found. A possible solution is to build up a new script by re-using code fragments for small parts of the task at hand. The code fragments can be accessed from a library of code fragments while writing the script from inside a text editor that supports snippet libraries. We developed such a library of code fragments--or snippets--for 20 popular text editors including the very popular Visual Studio Code, Atom, Sublime Text, vim, emacs, and Jupyter Notebook. We have included lexers where needed for syntax highlighting with colored text. This library is available on GitHub with instructions for installation on the Mac, Windows, and Linux operating systems. We expect that the library will lower motivational barriers to writing scripts to make figures in PyMOL and thereby help many PyMOL users become more productive at using PyMOL to do structural analyses and generate figures for publication. 

View Proposal 258

Author

Blaine Mooers, Universtiy of Oklahoma Health Sciences Center Oklahoma City, OK 

Additional Author

Marina Brown, University of Oklahoma Health Sciences Center Oklahoma City, OK 

Infusible Nuclear Fuel Synthesis beyond 25,000 °C for Far Deep Cosmic-Space Explorations

Every carbon-allotrope sample is suitable to be directly and clearly atomized into overheated free carbon atoms which are promoted and shifted towards highly excited electronic states. However, the ubiquitous extended practices to construct great-sized (low density ↔ colder plasma) generators allow the achievement of operative temperatures which are struggling too low for the always desirable finest and efficient atomization targets. All the attempts to strip-out denuded atoms are unavoidably linked to many cumbersome working-parameters needed for high chemical synthesis demands but the energy availability to do this is always too low. The straightforward pyramidalization processes of Gillespie-governed tetrahedral carbon atoms largely evade and surpass the often encountered carbo-graphitization reactions – but at extremely high temperatures only. In addition, the 2D-stacked graphite with its unfilled structural space-gaps and weakly interacting van der Waals forces constitutes the well known matrix for nuclear carbo-moderators – however, this cheap material unavoidably affects its thermal conductivity inside the fissionable fuel-pellets. On the other hand the isotropically distributed and spidery interlinked tetrahedral amorphous (ta-C) carbon atoms work better: their uninterrupted chains of momentum transfers minimize the elastic vibration dispersions. The synthetic non-stoichiometric 3D carbo-actinide fuel remains porous, permeable for rapid out-gassing of hot gases-debris as the massive isotope 135Xe, the most powerful known neutron poison, which rises up from radionuclide fissions and blocks the fission chain reactions. These exotics disclose new pathway-synthesis possibilities which are far out from everyday practices. The Bosonic properties of microwave photons inside the rectangular wave-guide resonators allows to achieve cumulative actions by highly localized electromagnetic (E.M.) peak-effects via oriented-fields convolution into a specific space-tine point. Volatile actinide/trans-actinide halide compounds (MX3, X = Br, etc.) are rapidly co-evaporated together with sharply and blistery gasified carbon species. At high temperatures they are thrust into a narrow quartz tube which passes orthogonally and throughout the drilled borehole into the flat walls of a rectangular waveguide resonator - 3D optimized cavity-coupler tuned up to 5.8 GHz. Here, the (E.M.) energy density and the peak-effects are maximized. The inlet low-temperature plasma is quickly shifted into high (E.M.) fields-zone to become more and more ionized by powerfully accelerated free electrons -even beyond 25,000 °C. The excited carbon atoms are expanded hypersonically into a vacuum trap to lose their high momenta via inelastic collisions against the chamber walls. The rapid phononic thermalization processes through dendritic (ta-C) carbon chains promote the growth of a spidery-amorphous but porous metal-carbide fuel-matrix – suitable for high powering in deep cosmic space mining and explorations. 

View Proposal 164

Author

Boris Udovic Sezana

Finding Nearest Neighbors in Crystallography with NearTree

Crystallography involves analysis of distances among points in several spaces: 3-dimensional real and reciprocal spaces, 1-, 2-, 3-, 4-, 5-, and 6- dimensional spaces of lattice parameters, and higher dimensional spaces in which those spaces may be embedded. In any or all of these spaces we may need to find one or more nearest neighbors, one or more farthest neighbors, centroids, or clusters. All of these tasks need efficient data structures with appropriate functions to allow us to implement efficient searches. NearTree is an implementation of a solution to the nearest neighbor problem. It is based on the algorithm described by Kalantari and McDonald in 1983. The mechanics of NearTree has replaced their complex operation with recursion. Also known as the post office problem, nearest neighbor searches arise in many contexts, including many that are familiar to crystallographers. NearTree is based on a binary tree structure. It is simple to use, and in practice it is found to operate with good speed. For the average dataset, insertion of a new data point has complexity O(n ln(n)). Retrieval of the nearest data point has complexity O(n). That means that NearTree's operation is optimal! In general, optimal algorithms will perform better than any others, at least for sufficiently large datasets; sufficiently large is often fairly small. NearTree is designed to use an external distance measure. It can work without prior knowledge of the dimensionality of the underlying data space, and can be used as a tool to help discover local Hausdorff dimensions. All post office problems need to deal with Bellman's "Curse of Dimensionality," which makes searches in higher dimensions more challenging than searches in lower dimensions. In our experience, we commonly use NearTree for three and six dimensions, but we have used NearTree for higher dimensions, up to 36 in the case of 6x6 matrices. One of the design objects of NearTree is ease of use. Only a few function calls, typically 2 or 3, are necessary to create a NearTree. A single function call will return the nearest neighbor. Besides the nearest neighbor, NearTree provides several other search functionalities. Farthest neighbor, those within a sphere, and those within an annulus are some of the additional search modes. Among the current practical crystallographic uses for NearTree are analysis of atomic bonding in RasMol, searching with SAUC for close cell parameters matches in the PDB or COD for molecular replacement, and ad hoc contact searches. Our current work includes analysis of cell clusters in serial crystallography. Andrews, Larry. "A template for the nearest neighbor problem." C/C++ Users Journal 19, no. 11 (2001): 40 -- 49. Andrews, Lawrence C., and Herbert J. Bernstein. "NearTree, a data structure and a software toolkit for the nearest‐neighbor problem." J. Appl. Cryst. 49, no. 3 (2016): 756-761. Bellman, Robert. "Curse of dimensionality." Adaptive control processes: a guided tour. Princeton, NJ 3 (1961): 2. Hausdorff, Felix. "Dimension und äußeres Maß." Mathematische Annalen 79, no. 1-2 (1918): 157-179. Kalantari, Iraj, and Gerard McDonald. "A data structure and an algorithm for the nearest point problem." IEEE Transactions on Software Engineering 5 (1983): 631 -- 634. McGill, Keith J., Mojgan Asadi, Maria T. Karakasheva, Lawrence C. Andrews, and Herbert J. Bernstein. "The geometry of Niggli reduction: SAUC – search of alternative unit cells." J. Appl. Cryst. 47, no. 1 (2014): 360 -- 364. 

View Proposal 339

Author

Lawrence Andrews, Ronin Institute Kirkland, WA 

Additional Author

Herbert Bernstein, Ronin Institute for Independent Scholarship, c/o NSLS-II, Brookhaven National Lab, Bldg 745 Bellport, NY 

Electronic Structure and Site Dynamics in Copper Doped Tutton Salts

Temperature dependent Electron Paramagnetic Resonance (EPR) has long been used to evaluate the dynamic Jahn-Teller behavior of copper ions in doped double metal hexahydrate sulfates (Tutton salts). Our recent EPR analysis of doped cadmium creatininium sulfate has expanded these investigations to include metal-organic Tutton salt analogues. The observed range of measured JT and EPR spectral parameters for the Cu2+(H2O)6 complex in these crystals offers an opportunity to weigh the effect of the host crystal environment on the site dynamics and electronic structure of the copper. To this end, computational chemistry calculations were undertaken for a series of Tutton salts and analogues in order to assess the influence of the host crystalline electric field on the copper unpaired electron wavefunction. DFT computations were performed on clusters centered on the metal-hexaaquo in order determine atomic charges from which electric field vectors and potentials were deduced at points along the copper-water bonds. Our early analysis shows a much higher electric potential in those Tutton systems which exhibit a more pronounced EPR temperature dependency and hence larger JT dynamic behavior. This reflects a stronger coupling to the lattice in these systems. Also, a rough correlation was found between the unpaired electron dx2-y2 orbital spin percentage and the magnitude of the host crystal electric potential. The relationship between the two is being further studied. This work advances our understanding of copper dynamics in biological crystals and how structural and environmental electronic features may facilitate this process. 

View Proposal 419

Author

Jacqueline Vitali, Cleveland State University Lakewood, OH 

Additional Author

Michael Colaneri, SUNY Old Westbury Old Westbury, NY 

Understanding the evolution of SARS-CoV-2 non-structural protein 15 (Nsp15) in three dimensions (3D)

SARS-CoV-2 is the coronavirus responsible for the global COVID-19 pandemic. There is currently little information on SARS-CoV-2 and the proteins encoded by its positive-strand RNA genome. Our research utilizes computational structural biology tools to explore the evolution of SARS-CoV-2 proteins in 3D. As part of a virtual summer research experience with the RCSB PDB, we studied how SARS-CoV-2 proteins evolved during the first six months of the COVID-19 pandemic by exploring amino acid sequence and 3D atomic-level structure using various structural bioinformatics tools, including Clustal Omega (www.ebi.ac.uk/Tools/msa/clustalo/) for sequence alignments and phylogenetic trees; Mol* (molstar.org) for 3D molecular visualization; and Foldit (fold.it) for structural/energetic effects of sequence mutations. Non-structural protein 15 (Nsp15) occurs near the C-terminus of the SARS-CoV-2 polyprotein 1ab that is expressed during the early stages of viral infection. Following cleavage from this polyprotein by the Main Protease (Nsp5), Nsp15 assembles into a symmetric hexamer that functions as a uridylate-specific endoribonuclease. While not essential for viral replication in the laboratory setting, conservation of Nsp15 amongst coronaviruses implies that it plays important roles in the virus life cycle. More than 300 unique mutant forms of Nsp15 detected during the first six months of the pandemic were analyzed to determine differences from the wild-type protein. Investigation of the mutation data could provide insights relevant to discovery and development of drugs to combat SARS-CoV-2. This work was supported by an NSF REU. RCSB PDB is funded by the National Science Foundation (DBI-1832184), the US Department of Energy (DE-SC0019749), and the National Cancer Institute, National Institute of Allergy and Infectious Diseases, and National Institute of General Medical Sciences of the National Institutes of Health under grant R01GM133198. 

View Proposal 450

Author

Sophia Staggers, 1999 Lanham, MD 

Additional Author(s)

Christine Zardecki, Rutgers Proteomics, RCSB Protein Data Bank Piscataway, NJ 
Sagar Khare, Institute for Quantitative Biomedicine
Stephen Burley, RCSB Protein Data Bank, Rutgers University Piscataway, NJ 

Structural Analysis of Severe Acute Respiratory Syndrome Coronavirus-2 Proteins: Exploring Mutations in Nsp13

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), discovered in December 2019, caused the COVID-19 global pandemic. SARS-CoV-2 belongs to the family, Coronaviridae, which is composed of positive-stranded RNA viruses. These viruses are known to have one of the largest RNA viral genomes, which consists of approximately thirty-thousand base pairs. The SARS-CoV-2 genome encodes both non-structural proteins, which assist in replication of the virus upon infection, and various structural and assembly proteins. As part of a virtual summer research experience with the RCSB PDB, we studied how SARS-CoV-2 proteins protein evolved during the first six months of the COVID-19 pandemic by exploring amino acid sequence and 3D atomic-level structure using various structural bioinformatics tools, including Clustal Omega (www.ebi.ac.uk/Tools/msa/clustalo/) for sequence alignments and phylogenetic trees; Mol* (molstar.org) for 3D molecular visualization; and Foldit (fold.it) for structural/energetic effects of sequence mutations. The focus of this poster is SARS-CoV-2 non-structural protein 13 (Nsp13), a 596-residue protein consisting of five domains. Nsp13 functions as a helicase, unwinding double-stranded RNA. Helicase activity depends on NTP hydrolysis, catalyzed by six conserved active site residues. Nsp13 synergizes with the viral RNA-dependent RNA polymerase, a heterotetramer consisting of once copy of Nsp7, two copies of Nsp8, and one copy of Nsp12. Nsp13 represents a potential target for discovery and development for small molecules that combat SARS-CoV-2. Studying the structure of this protein will enhance our understanding of its mechanism of action and ways to inhibit the enzyme. 

View Proposal 452

Author

Brea Tinsley, Youngstown State University Warren, OH 

Additional Author(s)

Stephen Burley, RCSB Protein Data Bank, Rutgers University Piscataway, NJ 
Christine Zardecki, Rutgers Proteomics, RCSB Protein Data Bank Piscataway, NJ 
Sagar Khare, Institute for Quantitative Biomedicine

Mapping COVID-19 Mutations in 3D: How SARS-CoV-2 has evolved during the first 6 months of the global pandemic

The World Health Organization reported that the number of COVID-19 cases worldwide was over 10 million with over 500,000 deaths as of June 30, 2020. The causative agent of COVID-19, SARS-CoV-2, has a very long single-strand, positive sense, 5'-capped RNA genome that encodes ~30 proteins. As the virus spread worldwide following its exit from central China and viral genomes isolated from infected individuals were sequenced, many mutations of viral proteins were observed. Studying mutations of key viral proteins can give insight into the virus life cycle and may impact discovery and development of new antiviral drugs and vaccines. In order to do this, our team, as part of a virtual summer research experience with the RCSB PDB, studied how SARS-CoV-2 proteins evolved during the first six months of the COVID-19 pandemic. This was done by exploring amino acid sequence and 3D atomic-level structure using various structural bioinformatics tools, including Clustal Omega (www.ebi.ac.uk/Tools/msa/clustalo/) for sequence alignments and phylogenetic trees; Mol* (molstar.org) for 3D molecular visualization; and Foldit (fold.it) for structural/energetic effects of sequence mutations. One key protein for SARS-CoV-2 is non-structural protein 14 (Nsp14). This protein supports both viral genome capping with a 5' 7-methyl-guanine cap and proofreading. It shares 95% sequence identity with Nsp14 pof SARS-CoV, demonstrating a high level of conservation. More than 300 unique variants of Nsp14 were modeled using the structural bioinformatics tools and analyzed using PyRosetta. We then identified certain mutations for further study on the basis of the affected amino acid's role in protein function and its location within the 3D structure. 

View Proposal 451

Author

Aaliyah Khan Takoma Park, MD 

Additional Author(s)

Christine Zardecki, Rutgers Proteomics, RCSB Protein Data Bank Piscataway, NJ 
Stephen Burley, RCSB Protein Data Bank, Rutgers University Piscataway, NJ 
Sagar Khare, Institute for Quantitative Biomedicine

Delving Into COVID-19 “Seams”: Examining the Structural Fabric of SARS-CoV-2

The year 2019 and 2020 took an unprecedented turn as SARS-CoV-2 (COVID-19) ravaged the world, taking over half a million lives (as of July 2020), leaving vulnerable communities to take the hardest hits, exacerbating systemic injustices towards minorities (including decreased access to healthcare), and damaging economies. By examining proteins and their respective mutations in SARS-CoV-2, a better understanding of its structural biology can aid in drug and vaccine discovery. Further applications of a deepened structural understanding of SARS-CoV-2 include assisting in broader research efforts and valuable public health efforts to mitigate and prevent harm caused by SARS-CoV-2 and other coronaviruses worldwide. As part of a virtual summer research experience with the RCSB PDB, we studied how SARS-CoV-2 proteins protein evolved during the first six months of the COVID-19 pandemic by exploring amino acid sequence and 3D atomic-level structure using various structural bioinformatics tools, including Clustal Omega (www.ebi.ac.uk/Tools/msa/clustalo/) for sequence alignments and phylogenetic trees; Mol* (molstar.org) for 3D molecular visualization; and Foldit (fold.it) for structural/energetic effects of sequence mutations. The focus of this poster is SARS-CoV-2 Orf7a, a viral protein that interferes with N-linked glycosylation of the cellular protein BST-2, an inhibitor of coronavirus release (Taylor et al. 2015). Orf7a has also been shown to arrest cells in the G0/G1 cell checkpoint during SARS-CoV infection, thereby preventing cell cycle progression. The G0/G1 cell checkpoint is a phase in the cell division process wherein DNA is checked for damage before allowing progress into the S phase. If DNA damage cannot be repaired cell death ensues. Prevention of cell cycle progression is thought to provide more time for coronaviruses to replicate at higher rates with increased nucleotide pools and allow for higher virus pathogenicity (Yuan et al. 2005). Studying Orf7a can provide insights into SARS-CoV-2 pathogenesis, including what proteins are involved in regulating viral propagation and what SARS-CoV-2 proteins affect host cell cycle regulation. RCSB PDB is funded by the National Science Foundation (DBI-1832184), the US Department of Energy (DE-SC0019749), and the National Cancer Institute, National Institute of Allergy and Infectious Diseases, and National Institute of General Medical Sciences of the National Institutes of Health under grant R01GM133198. 

View Proposal 453

Author

Luz Alfaro Elizabeth, NJ 

Additional Author(s)

Christine Zardecki, Rutgers Proteomics, RCSB Protein Data Bank Piscataway, NJ 
Sagar Khare, Institute for Quantitative Biomedicine
Stephen Burley, RCSB Protein Data Bank, Rutgers University Piscataway, NJ 

Lattice dynamics of antimony under pressure

The group Va elements, with the only exception of nitrogen, crystallise in the rhombohedral A7 structure. It comes from a small distortion with respect to a simple cube. The distorted structure leads to twice as many atoms in the primitive cell, inducing a gain in the electron energy with a connected gap opening, called a Peierls distorted structure. Under pressure, the distortion is reduced, but remains finite, as antimony transforms through a series of highly complex structure, before adopting as last the BCC (body-centred cubic) phase. Through the combination of diffuse and inelastic x-ray scattering compared with ab-initio calculation and a symmetry-based phenomenological model of the phase transitions, the dynamics behaviour approaching the transition is analysed. The main diffuse scattering features and, to some extent, the peculiarities in the lattice dynamics of the A7 phase will be explained by the instability of the primitive cubic network with respect to a correlated displacement. 

View Proposal 458

Author

Arianna Minelli

Additional Author(s)

Sofia Michaela Souliou, Institut for solid state physics, Karlsruhe institute of technology
Aldo Humberto Romero, Department of Physics and Astronomy, West Virginia University WV 
Vladimir Dmitriev, European Synchrotron Radiation Facility (ESRF) Grenoble
Alexei Bosak, European Synchrotron Radiation Facikity (ESRF) Grenoble