XXII IUCr Congress and General Assembly
Madrid, Spain, August 22-30, 2011
Continued from Volume 20, Number 1
|Keynote speaker (KN01) Tomitake Tsukihara with chair Yasushi Kai.||Keynote speaker (KN04) Peter D. Kwong with chair David Stuart.||Keynote speaker (KN25) Christiane Schaffitzel with chair Daniela Stock.||Keynote speaker (KN36) Isabelle Mirebeau with chair J. L. García Muñoz.|
Solid-state reactions, phase transition
Solid-state reactivity (MS60)
The microsymposium highlighted the power and versatility of X-ray diffraction, at non-ambient conditions, in unraveling the interplay between structural features and chemical-physical properties during solid-state transformations. A. Fuertes (ICMAB, Spain) showed how the physical properties of perovskite oxynitrides can be modulated by tuning synthesis conditions, counter-ion nature and anion ordering. In situ XRPD experiments allowed K. Chapman (APS, USA) to demonstrate the feasibility of PDF analysis to investigate reactions at the atomic scale, focusing on lithium-ion batteries and catalytically active metal nanoparticles, and L. Barrio (CSIC, Spain) to investigate the behavior of copper/iron spinel catalysts in the presence of reducing gases. Finally, S. Pagola (College of William and Mary, USA) and I. A. Tumanov (Russia) introduced the audience to the world of mechanochemical synthesis: Pagola demonstrated the possibility of isolating and characterizing elusive charge-transfer salts; Tumanov described the potentiality of a home-made device for step-by-step energetic and structural studies of mechanochemical reactions undergone by organic compounds.Chairs: Simona Galli, John Parise
Solid-state photochemistry (MS80)
After a short introduction to the subject, P. R. Raithby (U. of Bath, UK) described studies of reversible and irreversible photoactivated reactions of transition metal complexes. He showed the reversible transformation of a metal nitro linkage isomer to the nitrite linkage isomer in a single crystal. When the temperature is raised above 200 K the metasable nitrite isomer changes to the nitro isomer. To illustrate the irreversible reaction he demonstrated how the conversion of a photochromic compound can be increased by connecting the photochromic system to Pt or Au.
M. Scholz (Max-Planck-Inst., Germany) described the real-time dynamics of solid molecular switches investigated by ultrafast pulsed X-ray radiation and discussused averaging, integration methods and intensity corrections. Y. Ozawa (Chuo U., Japan) described the changes observed in the photoexcited state of luminescent hexanuclear d10 complexes of Cu and Ag. J. M. Cole (U. of Cambridge, UK) talked about time-resolved photocrystallography of ruthenium sulfur-dioxide complexes and the transformation from Ru-SO2 to the metastable Ru-OSO isomer, and claimed that the last photoisomer is not metastable at 100 K. A. Sekine (Tokyo Inst. of Tech., Japan) showed a method to control photochromic reactivity by bridging the photochromic compound to cobaloxime.Chairs: Pilar Gomez-Sal, Menahem Kaftory
Pressure-induced phase transitions (MS40)
Experimental and theoretical investigations described in this microsymposium included solid-solid phase transitions, amorphization and melting. K. Takemura (NIMS, Japan) reported on the pressure-temperature phase diagram of the intermetallic Na-In compounds and its relation to other binary phases. W. Crichton (ESRF, France) showed how the structures of new high-pressure phases that are difficult to solve due to the limited amount of information could be determined using topological features of the known structures. E. Kudrenko (ISSP, Russia) presented amorphization of rare-earth molybdates in which the observed memory glass effect is due to the incomplete amorphization of the samples even at the highest pressures. J. Ruiz-Fuertes (U. de València, Spain) demonstrated that in contrast to the predictions from theoretical models, the Jahn-Teller effect around the Cu2+ ions in CuWO4 is not quenched at high pressures, although it is reduced. B. Boates (LLNL, USA) presented a theoretical phase diagram of CO2. Both the liquid and solid phases were considered and the melting curve was calculated to 150 GPa. A novel method for the calculation of liquid free energies was introduced.Chairs: Karen Friese, V. Brazhkin
Powder diffraction at the nanoscale (MS18)
Talks in this session covered a range of different nanosized materials and characterization methods. V. Petkov (Central Michican U., USA) presented the fundamentals of the Pair Distribution Function (PDF) and an overview of its application on gold, CdSe and other semiconductors, highlighting the importance of extracting information from diffuse scattering on high-energy diffraction patterns. D. Keen (Science and Technology Facilities Council, UK) used PDF analysis to describe the in situ amorphization of two technologically relevant compounds (zirconium tungstate and ZIF-4), and compared their structural changes when amorphization is pressure- and temperature-induced. A multi-scale characterization of a perylene diimide derivative film was presented by S. Milita (IMM CNR, Italy) to correlate structure and electronic performances. Ab initio structure solution from powder data provided the molecular organization in the bulk and grazing incidence X-ray diffraction experiments were used to obtain information on the nanoscale film structure. D. Schaniel (U. de Lorraine, France) combined small- and wide-angle neutron diffraction and Debye function analysis to identify single photo-switchable GuNP molecules embedded in a porous SiO2 matrix, and to estimate average pore size and filling factor. Finally, treatment of a 2D paracrystallinity effect with the Debye equation was described by A. Cervellino (Paul Scherrer Inst., Switzerland) who used it to model a difficult-to-interpret peak broadening in a polymeric metal-carbonyl sample.Chairs: Antonella Guagliardi, Yuri Andreev
Atomistic and electronic structures of nanomaterials (MS65)
V. Keast (U. of Newcastle, Australia) discussed theoretical aspects of electron energy loss spectroscopy (EELS), including the effect of gold cluster size on the shape of its valence loss EELS. The overall shape of spectral features obtained from ab initio calculations for large clusters approached Mie theory. For clusters below 30 atoms the internal structure of the cluster had the strongest effect on the spectra, whereas for larger clusters the outer shape of the cluster was the most important. C. H. Chen (Nat'l Taiwan U., Taiwan) presented results on EDX chemical mapping in a JEOL 2100 F with a probe with corrected spherical aberration. The instrument appears to have excellent stability and can produce chemical maps with atomic resolution. Chen also discussed the advantages and setbacks of EDX and EELS. S. van Aert provided a detailed account of a new method for atomic resolution (discrete) electron tomography. She uses statistical methods to 'count' atoms of a given type in projection annular dark-field scanning TEM images. Just two projections are needed to reconstruct the internal structure of a nanoparticle down to individual atoms when using prior knowledge about the particle. G. Botton (McMaster U., Canada) described many examples of EELS at very high spatial and energy resolution. His most impressive example came from the study of carbon nanotubes for which EELS spectra collected from the sides of the nanotube, where the incident beam is perpendicular to the pi* orbitals, differed significantly from the center of the nanotube where the incident beam is parallel to the pi* carbon orbitals. W. F. Pong (Tamkang U., Taiwan) discussed how analysis of the electronic properties of a nanomaterial, (Au nanocrystals in SiOx), was used to provide insight into photoconductivity.Marek Malac, Quan Li
Semi-conducting, energy and graphic materials
Energy-related materials (MS39)
The session covered energy-related materials including: solid oxide fuel cells, dyes and solar cells, batteries, nuclear waste, thermoelectrics, and hydrogen storage.
The first lecture was given by M. Bowden (Pacific Northwest Nat'l Lab., USA) on 'The structure and dynamics of hydrogen storage materials based on boron and nitrogen' in which he paid special attention to the structural characterisation of ammonia borane, which is especially attractive from the point of view of hydrogen storage due to its 19.6wt.% H2.
In 'Synchrotron, X-rays and neutrons as essential tools in Li battery research: new structures and new properties', C. Masquelier (LRCS-UPJV, France) described how fine structural characterisation in situ provides understanding of electrochemical mechanisms at the atomic level. Specific examples dealt with lithium iron phosphate and silicate.
L. Suescun (Cryssmat Lab-DETEMA, Uruguay) described 'A new homologous series of oxygen vacancy ordered strontium manganese perovskites' relevant to solid oxide fuel cells. D. Viterbo (Dista-U. Piemonte Orientale, Italy) discussed 'Polyene-diphenylaniline D5 dyes and their role in the efficiency of DSSC solar cells'. He described the crystal structure of D5 (a polyene aniline-based dye), and a very interesting chemometric approach to study the effect of CDCA anti-aggregation studies was presented. C. Stephan (Helmholtz-Zentrum Berlin, Germany) spoke about 'Cation distribution in off-stoichiometric CuInSe2 and CuGaSe2', which are used as absorber layers in thin-film solar cells. Neutron powder diffraction and anomalous X-ray diffraction experiments made possible the determination of the dominant defect types which lead to enhanced understanding of the complex electronic properties of these materials.
In almost all talks, combinations of techniques (i.e. in situ diffraction with electrochemistry) that allow structural data acquisition in real time were employed.Chairs: William I. F. David, M. Rosa Palacín
Graphitic materials (MS52)
The field of graphitic materials has developed rapidly with the discovery of fullerenes in 1985 and intense research on carbon nanotubes and graphene. The discovery of fullerenes and groundbreaking experiments regarding graphene garnered Nobel prizes, in 1996 and in 2010.
The talks of the MS concerned studies of new members of the fullerenes, carbon nanotubes and graphene family using electron microscopy, X-ray diffraction and inelastic neutron scattering. S. Rols (Inst. Laue-Langevin, France) discussed the rotational and translational dynamics of fullerenes inside carbon nanotubes in terms of confinement and low-dimensionality effects. J. Meyer (U. of Vienna, Austria) reported HRTEM studies of graphene with dopants and defects. A. Parlett (UK) examined the deposition behavior of organometallic complexes with pyrene-synthesized nano-graphene on a graphene substrate. J. Hodeau (CNRS, France) demonstrated that X-ray scattering resolved tomography is a powerful tool to investigate a multi-phased carbon system obtained by pressure-crush of C60; a new carbon phase with an unexpected short inter-layer distance was found. C. Bahtz (ESRF, France) discussed catalyzed carbon nanotube growth observed with in situ X-ray diffraction experiments.Chairs: Pascale Launois, Kazu Suenaga
Wide-band semiconductor and other crystals used in optoelectronics (MS28)
The Microsymposium included five presentations covering (a) control of stresses and strains in GaN heteroepitaxy to achieve crack-free device-relevant GaN layers on Si (A. Krost, Germany) (b) a method for the determination of the densities of individual defect types in GaN layers, based on diffuse X-ray scattering and reciprocal space mapping (V. Holy, Czech Republic), (c) AlGaN and GaN layers grown on misoriented (off-axis) GaN substrates by metalorganic chemical vapour-phase epitaxy (MOVPE) (M. Leszczynski, Poland), (d) the dependencies of linear and non-linear electrooptic and photorefractive properties of LiNbO3 crystals doped with Mg, Fe, Zn, or Hf (M. Fontana, France) and (e) laser experiments for power scaling carried out with Yb:KLu(WO4)2 in the thin-disk configuration at high pump powers that showed a significant improvement in thermal management due to the one-dimensional heat flow (M. C. Pujol, Spain).Chairs: Ewa Talik and Krystian Roleder
Structural implications in catalytic processes (MS31)
This session addressed the relationship between structure, dynamics and composition of catalysts and the mechanisms of a catalytic process, with emphasis on the trapping of intermediates. Materials discussed were heterogeneous catalysts (zeolites, metal oxides) and homogeneous catalysts from biological (enzymes) and chemical (nickel indenyl derivatives) systems. J. A. Martens (Katholieke U. Leuven, Belgium) discussed the effect of partial exchange of Na+ for Ru3+ in zeolite Y on cation redistribution and the performance of the resulting material for NOx trapping from exhaust gases, and proposed a possible catalytic reduction/oxidation mechanism for NOx scavenging. C. Weidenthaler (Max-Planck-Inst. für Kohlenforschung, Germany) addressed the optimization of iron and molybdenum oxide-based catalysts for ammonia decomposition, a relevant process for dihydrogen production, by means of a specially designed XRPD chamber, which allowed in situ insight into the different crystalline phases formed during the catalytic process. C. S. B. Gomes (Inst. Superior Técnico, Portugal) systematically studied the impact of the donor ability of the XPh3 ligands on the indenyl ligand distortion of [(indenyl)Ni(XPh3)Y] (X = P, As, Sb; Y = Cl, Br, I) systems and their eventual effect on the catalytic performance on styrene oligomerisation reactions. B. Stec (Sanford-Burnham Medical Research Inst., USA) discussed the kinetic and thermodynamic difficulties of trapping intermediates in enzyme catalytic reactions and presented different methods for achieving this, by means of blocking a particular conformation using changes in temperature and pH or the addition of an excess of the reaction product. Finally, N. Kamiya (Osaka City U., Japan) described the high-resolution structure of Photosystem II that revealed the details of the Mn4CaO5 catalytic active site, in which Ca and Mn belonged to the same cluster. The distortion introduced by the Ca2+ ion and its weak coordination to O2− and H2O appears to facilitate O—O bond formation, giving rise to a new mechanism proposal explaining O2 evolution.Chairs: María José Calhorda, Jorge A. Rodríguez-Navarro
Art and forensics
Powder diffraction methods in archaeometry (MS46)
This session highlighted crystallographic analysis of artworks and ancient materials with powder diffraction and micro-diffraction.
C. Cardell (U. of Granada, Spain) presented a talk entitled 'X-ray diffraction methods as a complementary tool for analyses of historical objects', characterizing various samples of historical objects using different XRD techniques. Among them X-ray thermo-diffraction was found to be a powerful method for studying phase transitions in various materials. Samples originating from Alhambra were analyzed by means of micro-XRD. Finally, the benefits of combining XRD with other analytical techniques (Raman, SEM/EDS) were clearly highlighted.
P. Martinetto (CNRS-UJF, Grenoble, France) described 'Synthetic or manufactured ancient pigments studied by means of synchrotron radiation-based methods' that focused on studying ancient pigments by means of synchrotron radiation. The complex structural features of Maya Blue, an organo-clay compound based on the palygorskite-hosted indigo molecule, was described, as were analogous materials based on zeolite-hosted pigmenting molecules. She descibed chemical and structural investigations of Prussian blue using PDF analysis that demonstrated the relationship between degradation processes and crystal defects.
F. Grazzi (CNR, Sesto Fiorentino Italy), gave a talk entitled 'Quantitative characterization of Japanese ancient swords through time-of-flight neutron diffraction and energy-resolved neutron imaging' that was dedicated to the non-destructive characterization of materials used for manufacturing Japanese swords in different periods. Neutron diffraction was employed for determining the texture and the quantitative distribution of various steel phases in the blades. The data may be used to fingerprint sword-making processes in different periods and regions in ancient Japan.
C. Gervais (Smithsonian Inst., Washington DC, USA), spoke on 'Estimation of iron valences of Prussian blue pigment by anomalous X-ray diffraction'. XANES and XRD analyses led to better understanding of the processes of discoloration of the pigment. A. Rafalska-Łasocha (Jagiellonian U., Poland) presented 'XRPD studies of the objects of cultural heritage made of copper or its alloys' showing the successful application of X-ray powder diffraction and micro-diffraction to the study of copper and bronze artifacts. Several examples demonstrated the origin of the 'bronze disease' and the role of Cl− ions in propagating the degradation reaction.Chairs: Gilberto Artioli, Petr Bezdicka
X-ray absorption, diffraction and imaging in forensic science and ancient materials (MS91)
This microsymposium was organized jointly by the IUCr Commissions on Crystallography in Art and Cultural Heritage, X-ray Absorption Fine Structure and Powder Diffraction, to review developments in the application of X-ray absorption, diffraction and imaging techniques to the study of historical, archaeological, palaeontogical and forensic materials.
G. Artioli (U. of Padova, Italy) discussed archaeometrical approaches to the study of ancient materials. M. P. Morigi (U. Bologna, Italy) focused on the application of 3D computed tomography to the study of bronze and wooden statues, coffins, fossil skulls, paintings, and remains of forensic interest. She showed the potential for non-destructive investigation of unique artefacts, and medical and forensic applications.
K. Wallwork (Australian Synchrotron, Australia, 'Investigations of ancient Egyptian faience using XAS and powder diffraction') and F. d'Acapito (CNR-IOM-OGG, ESRF, France, 'Evidence of the role of Zn and Fe cations as dopants in lead antimonate yellow by XAS') described application of X-ray absorption fine structure to the study of archaeological glass.
A talk on 'Powder X-ray micro-diffraction in the forensic science', given by M. Kotrlý (Inst. of Criminalistics in Prague, Czech Republic), focused on the application of X-ray micro-diffraction to forensic problems involving materials ranging from drugs and paintings, to bullets and anthropological samples.Chairs: Simona Quartieri, J. Susini - substituted in Madrid by P. Bezdicka
Topological crystal chemistry
Topological correlations and crystal structure interconnections (MS09)
The advantage of abstracting from pure structure data to make use of a topological view for studying concrete and hypothetical classes of compounds was the main focus of this MS. The contributions showed that neglecting partially or fully information on geometry and symmetry proved to be useful for the systematic description and classification as well as for the prediction of crystal structures.
M. Schröder (U. of Nottingham, UK) demonstrated in his talk on 'Modulation of structures and gas storage properties in MOF materials' how such a view can be used to study the role of topological factors in the field of metal-organic frameworks, including different forms of interpenetration and possible consequences for the networks of the exchange of extra-framework cations. Results are promising for the design of new materials with attractive gas-storage properties, such as those with two kinds of cages (or gateways) shown in the figure.
E. Aleksandrov (Russia) reported in his talk 'Underlying nets in three-periodic coordination polymers' the principles of a classification method of coordination polymers performed automatically by the program package TOPOS, using topological properties of networks. The results of an exhaustive analysis of existing databases suggested the existence of restrictions to topological types for crystal structures according to the geometrical characteristics of coordination groups.
E. Gobechiya's (U. Leuven, Belgium) talk, 'The role of metal cations as template species in zeolite framework formation', discussed the possibilities of selective orientation of the crystallization reaction pathway, during or after synthesis, to a given zeolite topology.
O. Gagné (U. Manitoba, Canada) proposed in his talk, 'A new approach to crystal-structure prediction', an algorithm based on the application of bond-valence theories in association with information obtained from crystal structure databases to pick out acceptable candidate crystal structures corresponding to a given topology and chemical composition.
If it becomes possible in the long-term to define, a priori, ideal synthesis conditions leading to the formation of some crystal structures with a given chemical composition, it is clear that topological considerations will have a place in the solid-state chemist's tool-box.Hans-Joachim Klein and Jean-Guillaume Eon