Application-Driven Quantum and Statistical Physics. A Short Course for Future Scientists and Engineers. Volume 1: Foundations. Volume 2: Equilibrium. By Jean-Michel Gillet. World Scientific, 2018. Hardcover, price GBP 86.00 each. Volume 1: pp. 300, ISBN 978-1-78634-554-7. Volume 2: pp. 336, ISBN 978-1-78634-557-8.
(Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - January 28, 2020 Category: Chemistry Authors: Schwarz, K. Tags: book review quantum physics statistical physics book reviews Source Type: research
Quasicrystal-related mosaics with periodic lattices interlaid with aperiodic tiles
Quasicrystals, which have long-range orientational order without translational symmetry, are incompatible with the theory of conventional crystals, which are characterized by periodic lattices and uniformly repeated unit cells. Reported here is a novel quasicrystal-related solid state observed in two Al – Cr – Fe – Si alloys, which can be described as a mosaic of aperiodically distributed unit tiles in translationally periodic structural blocks. This new type of material possesses the opposing features of both conventional crystals and quasicrystals, which might trigger wide interest in theory, experiments and the po...
Source: Acta Crystallographica Section A - January 28, 2020 Category: Chemistry Authors: He, Z. Shen, Y. Ma, H. Sun, J. Ma, X. Li, H. Steurer, W. Tags: quasicrystals HAADF-STEM mosaics aperiodic tiling research papers Source Type: research
Phase of Pendell ö sung oscillations in X-ray dynamical diffraction for perfect crystals
Formulations are given for the intensities of transmitted and diffracted waves in the Laue case of a perfect crystal. This is applicable irrespective of the magnitudes of both the real and imaginary parts of the Fourier components of the crystal polarizability. The phase shift of the Pendell ö sung oscillations of the transmitted and diffracted waves is analyzed in detail for a symmetrical Laue case. The phase is determined to shift continuously from out of phase to in phase for absorbing crystals. (Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - January 28, 2020 Category: Chemistry Authors: Saka, T. Tags: X-ray diffraction dynamical theory Pendell ö sung oscillations phase Laue case research papers Source Type: research
Report of the Executive Committee for 2018
The report of the Executive Committee for 2018 is presented. (Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - January 23, 2020 Category: Chemistry Authors: Ashcroft, A.T. Tags: International Union of Crystallography IUCr Executive Committee Source Type: research
Twenty-Fourth General Assembly and International Congress of Crystallography, Hyderabad, India, 21 – 28 August 2017
(Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - January 22, 2020 Category: Chemistry Authors: Ashcroft, A.T. Tags: International Union of Crystallography IUCr General Assembly International Congress of Crystallography Source Type: research
pinkIndexer – a universal indexer for pink-beam X-ray and electron diffraction snapshots
A crystallographic indexing algorithm, pinkIndexer, is presented for the analysis of snapshot diffraction patterns. It can be used in a variety of contexts including measurements made with a monochromatic radiation source, a polychromatic source or with radiation of very short wavelength. As such, the algorithm is particularly suited to automated data processing for two emerging measurement techniques for macromolecular structure determination: serial pink-beam X-ray crystallography and serial electron crystallography, which until now lacked reliable programs for analyzing many individual diffraction patterns from crystals...
Source: Acta Crystallographica Section A - January 22, 2020 Category: Chemistry Authors: Gevorkov, Y. Barty, A. Brehm, W. White, T.A. Tolstikova, A. Wiedorn, M.O. Meents, A. Grigat, R.-R. Chapman, H.N. Yefanov, O. Tags: indexing pinkIndexer CrystFEL pink X-ray beam serial electron diffraction research papers Source Type: research
Quantum Theory of Materials. By Efthimios Kaxiras and John D. Joannopoulos. Cambridge University Press, 2019. Hardback, pp. 645. Price GBP 64.99, USD 89.99. ISBN 9780521117111.
(Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - January 9, 2020 Category: Chemistry Authors: Glazer, M. Tags: book review quantum theory materials book reviews Source Type: research
On the real combinations of cubes and octahedra
All the real combinations of cubes and octahedra (77657 in total) are enumerated and characterized by facet symbols and symmetry point groups. The most symmetrical polyhedra (with automorphism group orders not less than 6, 163 in total) are shown. It is assumed that they represent the most probable forms of natural diamond crystals. The results are discussed with respect to the Curie dissymmetry principle. (Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - January 9, 2020 Category: Chemistry Authors: Voytekhovsky, Y.L. Stepenshchikov, D.G. Tags: cubes octahedra symmetry point groups automorphism group order natural diamonds short communications Source Type: research
A combined model of electron density and lattice dynamics refined against elastic diffraction data. Thermodynamic properties of crystalline l-alanine
Thermodynamic stability is an essential property of crystalline materials, and its accurate calculation requires a reliable description of the thermal motion – phonons – in the crystal. Such information can be obtained from periodic density functional theory (DFT) calculations, but these are costly and in some cases insufficiently accurate for molecular crystals. This deficiency is addressed here by refining a lattice-dynamics model, derived from DFT calculations, against accurate high-resolution X-ray diffraction data. For the first time, a normal-mode refinement is combined with the refinement of aspherical atomic fo...
Source: Acta Crystallographica Section A - December 18, 2019 Category: Chemistry Authors: Sovago, I. Hoser, A.A. Madsen, A. Ø . Tags: thermal motion charge density thermodynamics modeling research papers Source Type: research
Refinement of organic crystal structures with multipolar electron scattering factors
In this study a comparison is presented of IAM and TAAM (transferable aspherical atom model), the latter with the parameters of the Hansen – Coppens multipole model transferred from the University at Buffalo Databank (UBDB). By this method, TAAM takes into account the fact that atoms in molecules are partially charged and are not spherical. Structure refinements were performed on a carbamazepine crystal using electron structure-factor amplitudes determined experimentally [Jones et al. (2018). ACS Cent. Sci. 4, 1587 – 1592] or modelled with theoretical quantum-mechanical methods. The results show the possibilities and l...
Source: Acta Crystallographica Section A - December 17, 2019 Category: Chemistry Authors: Gruza, B. Chodkiewicz, M.L. Krzeszczakowska, J. Dominiak, P.M. Tags: electron crystallography electron microscopy electron diffraction aspherical scattering factors structure refinement transferable aspherical atom model (TAAM) quantum crystallography micro-electron diffraction cryo-electron microscopy re Source Type: research
Cluster-mining: an approach for determining core structures of metallic nanoparticles from atomic pair distribution function data
A novel approach for finding and evaluating structural models of small metallic nanoparticles is presented. Rather than fitting a single model with many degrees of freedom, libraries of clusters from multiple structural motifs are built algorithmically and individually refined against experimental pair distribution functions. Each cluster fit is highly constrained. The approach, called cluster-mining, returns all candidate structure models that are consistent with the data as measured by a goodness of fit. It is highly automated, easy to use, and yields models that are more physically realistic and result in better agreeme...
Source: Acta Crystallographica Section A - December 17, 2019 Category: Chemistry Authors: Banerjee, S. Liu, C.-H. Jensen, K.M. Ø Juh á s, P. Lee, J.D. Tofanelli, M. Ackerson, C.J. Murray, C.B. Billinge, S.J.L. Tags: structural models nanoparticles clusters pair distribution functions data mining screening research papers Source Type: research
A real-space approach to the analysis of stacking faults in close-packed metals: G(r) modelling and Q-space feedback
An R-space approach to the simulation and fitting of a structural model to the experimental pair distribution function is described, to investigate the structural disorder (distance distribution and stacking faults) in close-packed metals. This is carried out by transferring the Debye function analysis into R space and simulating the low-angle and high-angle truncation for the evaluation of the relevant Fourier transform. The strengths and weaknesses of the R-space approach with respect to the usual Q-space approach are discussed. (Source: Acta Crystallographica Section A)
Source: Acta Crystallographica Section A - December 9, 2019 Category: Chemistry Authors: Longo, A. Giannici, F. Sciortino, L. Martorana, A. Tags: stacking faults pair distribution function Debye function analysis close-packed metals cobalt research papers Source Type: research
Inferring the one-electron reduced density matrix of molecular crystals from experimental data sets through semidefinite programming
Constructing a quantum description of crystals from scattering experiments is of great significance to explain their macroscopic properties and to evaluate the pertinence of theoretical ab initio models. While reconstruction methods of the one-electron reduced density matrix have already been proposed, they are usually tied to strong assumptions that limit and may introduce bias in the model. The goal of this paper is to infer a one-electron reduced density matrix (1-RDM) with minimal assumptions. It has been found that the mathematical framework of semidefinite programming can achieve this goal. Additionally, it convenien...
Source: Acta Crystallographica Section A - December 8, 2019 Category: Chemistry Authors: De Bruyne, B. Gillet, J.-M. Tags: one-electron reduced density matrix X-ray diffraction Compton diffusion semidefinite programming research papers Source Type: research
Monte Carlo simulation of coherently scattered photons based on the inverse-sampling technique
In this study, a novel Rayleigh scattering model using anomalous scattering factors based on the inverse-sampling technique is presented. Its performance was evaluated against other simulation algorithms in terms of simulation accuracy and computational efficiency. The computational efficiency was tested with a general-purpose Monte Carlo package named Particle Transport in Media (PTM). The evaluation showed that a Monte Carlo model using both atomic form factors and anomalous scattering factors for the angular distribution of photons (instead of the atomic form factors alone) produced Rayleigh scattering results in closer...
Source: Acta Crystallographica Section A - December 5, 2019 Category: Chemistry Authors: Muhammad, W. Liang, Y. Hart, G.R. Nartowt, B.J. Deng, J. Tags: Rayleigh scattering Monte Carlo simulation atomic form factors anomalous scattering factors total cross sections differential cross sections research papers Source Type: research
X-ray diffraction from strongly bent crystals and spectroscopy of X-ray free-electron laser pulses
The use of strongly bent crystals in spectrometers for pulses of a hard X-ray free-electron laser is explored theoretically. Diffraction is calculated in both dynamical and kinematical theories. It is shown that diffraction can be treated kinematically when the bending radius is small compared with the critical radius given by the ratio of the Bragg-case extinction length for the actual reflection to the Darwin width of this reflection. As a result, the spectral resolution is limited by the crystal thickness, rather than the extinction length, and can become better than the resolution of a planar dynamically diffracting cr...
Source: Acta Crystallographica Section A - December 5, 2019 Category: Chemistry Authors: Kaganer, V.M. Petrov, I. Samoylova, L. Tags: X-ray free-electron lasers X-ray spectroscopy bent crystals diamond crystal optics femtosecond X-ray diffraction dynamical diffraction research papers Source Type: research
