electronic reprint Acta Crystallographica Section B Structural Science (original) (raw)
Related papers
Philosophical Magazine Letters, 2009
To cite this Article Martinez-Garcia, J., Arakcheeva, A., Pattison, P., Morozov, V. and Chapuis, G. 'Validating the model of a (3 + 1)-dimensional incommensurately modulated structure as generator of a family of compounds for the Eu 2 (MoO 4 ) 3 scheelite structure',Philosophical Magazine Letters, To link to this Article:
Acta Crystallographica Section B-structural Science, 2002
The basic principles of a model predicting new lattices from a known crystal structure is described. The first of the two-step procedure consists in extracting one-or two-dimensional periodic fragments (PF) from the mother structure. In the second step, symmetry operators are added to the PFs in order to generate one or several new three-dimensional lattices consistent with the 230 space groups. Most of the examples are related to polymorphism, but relationships between racemic compounds and enantiomers, twinning and lamellar epitaxy phenomena are also exemplified.
Crystal Structure of a New Synthetic Homologue of the Switzerite Series
Doklady Chemistry, 2000
The switzerite homologous series includes natural and synthetic phases described by the general chemical formula Mn 3 ( PO 4 ) 2 × n H 2 O. The values n = 7 and 4 in this series correspond to the compositions of the minerals switzerite and metaswitzerite, respectively. One more homologous member, containing 0.5 water molecules, was synthesized and studied by us as part of a systematic study of 3 d transition-metal phosphates [1].
Journal of Applied Crystallography, 1996
The results of ab initio inorganic structure modelling are often in the form of Cartesian coordinates of atoms in a large, periodical and in general oblique simulation box containing hundreds to thousands of atoms. The contents of that box may correspond to a single crystal, a twin, a mixture of phases or a disordered block of matter. The problem of extracting corresponding crystallographic descriptions for single-crystal regions in the box, a necessary step in view of full quantum calculations and publication, is different from the familiar problem of extracting crystal symmetry and structure from experimental diffracted intensity data. The deductive computeraided method developed at the National Research Council of Canada over the years is based on eye identification of three pairs of atoms related by conjugate translations in the same single-crystal region on a stereo plot, followed by derivation of fractional coordinates for the atomic content of the corresponding primitive cell. Running this data through the MISSYM program discloses potential symmetry elements of the structure, with their corresponding crystallographic directions. These elements are then critically examined and accepted either as symmetry or pseudosyrnmetry on the basis of comparison of coordinate deviations between related atoms with the expected magnitude of thermal motion. All calculations described here can be performed with the NRCVAX system of programs.
The American Mineralogist crystal structure database
2003
A database has been constructed that contains all the crystal structures previously published in the and the University of Arizona. In addition to the database, a suite of interactive software is provided that can be used to view and manipulate the crystal structures and compute different properties of a crystal such as geometry, diffraction patterns, and procrystal electron densities. The database is set up so that the data can be easily incorporated into other software packages. Included at the website is an evolving set of guides to instruct the user and help with classroom education.
New Tricks of the Trade for Crystal Structure Refinement
ACS central science, 2017
Accurate crystal structures and their experimental uncertainties, determined by X-ray diffraction/neutron diffraction techniques, are vital for crystal engineering studies, such as polymorph stability and crystal morphology calculations. Because of differences in crystal growth and data measurement conditions, crystallographic databases often contain multiple entries of varying quality of the same compound. The choice of the most reliable and best quality crystal structure from many very similar structures remains an unresolved problem, especially for nonexperts. In addition, while crystallographers can make use of some professional software (i.e., Materials Studio) for structure refinement, noncrystallographers may not have access to it. In the present paper, we propose a simple method to study the sensitivity of the crystal lattice energy to changes in the structural parameters, which creates a diagnostic tool to test the quality of crystal structure files and to improve the low-q...