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Multiple Twinning (multiple + twinning)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Multiple twinning in cubic crystals: geometric/algebraic study and its application for the identification of the ,3n grain boundaries

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 1 2007
Cyril Cayron
Multiple twinning in cubic crystals is represented geometrically by a three-dimensional fractal and algebraically by a groupoid. In this groupoid, the variant crystals are the objects, the misorientations between the variants are the operations, and the ,3n operators are the different types of operations (expressed by sets of equivalent operations). A general formula gives the number of variants and the number of ,3n operators for any twinning order. Different substructures of this groupoid (free group, semigroup) can be equivalently introduced to encode the operations with strings. For any coding substructure, the operators are expressed by sets of equivalent strings. The composition of two operators is determined without any matrix calculation by string concatenations. It is multivalued due to the groupoid structure. The composition table of the operators is used to identify the ,3n grain boundaries and to reconstruct the twin related domains in the electron back-scattered diffraction maps. [source]

Quantitative microstructure characterization of self-annealed copper films with electron backscatter diffraction

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 2 2008
Karen Pantleon
Abstract Electron backscatter diffraction (EBSD) was applied to analyze cross sections of self-annealed copper electrodeposits, for which earlier the kinetics of self-annealing had been investigated by in-situ X-ray diffraction (XRD). The EBSD investigations on the grain size, grain boundary character and crystallographic texture of copper films with different thicknesses essentially supplement results from in-situ XRD. Twin relations between neighboring grains were identified from the orientation maps and the observed twin chains confirm multiple twinning in copper electrodeposits as the mechanism of microstructure evolution at room temperature (self-annealing). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A non-twinned polymorph of CaTe2O5 from a hydrothermally grown crystal

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2008
Matthias Weil
In contrast with the multiple twinning and/or domain formation found in the mica-like polymorphs of CaTe2O5, calcium pentaoxidoditellurate(IV), that have been prepared by solid-state reactions and for which complete structure determinations have not been successful up to now, the crystal structure of a hydrothermally grown phase was fully determined from a non-twinned crystal. The structure is made up of alternating layers of Ca2+ cations and of 2,[Te2O5]2, anions stacked along [100]. The lone-pair electrons E of the TeIV atoms are stereochemically active and protrude into channels within the anionic layer. In comparison with analogous MIITe2O5 structures (M = Mg, Mn, Ni or Cu) with ditellurate(IV) anions that are exclusively made up of corner-sharing TeOx (x = 3,5) polyhedra resulting in flat 2,[Te2O5]2, layers, the anionic layers in CaTe2O5 are undulating and are built of corner- and edge-sharing [TeO4] polyhedra. [source]