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17-571: Acta Crystallographica has been noted for the high quality of the papers that it produces, as well as the large impact that its papers have had on the field of crystallography. The current six journals form part of the journal portfolio of the IUCr, which is completed by the Journal of Applied Crystallography , the Journal of Synchrotron Radiation , the open-access IUCrJ and the open-access data publication IUCr Data . Acta Crystallographica

34-526: A mathematical method of characterization. Point defects are defects that occur only at or around a single lattice point. They are not extended in space in any dimension. Strict limits for how small a point defect is are generally not defined explicitly. However, these defects typically involve at most a few extra or missing atoms. Larger defects in an ordered structure are usually considered dislocation loops. For historical reasons, many point defects, especially in ionic crystals, are called centers : for example

51-500: A role also in solid materials, e.g. leading to the self-healing of cracks . A successful mathematical classification method for physical lattice defects, which works not only with the theory of dislocations and other defects in crystals but also, e.g., for disclinations in liquid crystals and for excitations in superfluid He, is the topological homotopy theory. Density functional theory , classical molecular dynamics and kinetic Monte Carlo simulations are widely used to study

68-499: A stack of paper is apt: if a half a piece of paper is inserted in a stack of paper, the defect in the stack is only noticeable at the edge of the half sheet. The screw dislocation is more difficult to visualise, but basically comprises a structure in which a helical path is traced around the linear defect (dislocation line) by the atomic planes of atoms in the crystal lattice. The presence of dislocation results in lattice strain (distortion). The direction and magnitude of such distortion

85-449: A vacancy in many ionic solids is called a luminescence center, a color center, or F-center . These dislocations permit ionic transport through crystals leading to electrochemical reactions. These are frequently specified using Kröger–Vink notation . Line defects can be described by gauge theories. Dislocations are linear defects, around which the atoms of the crystal lattice are misaligned. There are two basic types of dislocations,

102-506: Is a peer-reviewed scientific journal published by Wiley-Blackwell on behalf of the International Union of Crystallography . It was established in 1968 with André Guinier as the founding editor. The journal covers the application of crystallography and crystallographic techniques. William Parrish (1914–1991) chaired the committee that started the journal. The Journal of Applied Crystallography publishes articles on

119-558: Is abstracted and indexed in: Crystallographic defect A crystallographic defect is an interruption of the regular patterns of arrangement of atoms or molecules in crystalline solids . The positions and orientations of particles, which are repeating at fixed distances determined by the unit cell parameters in crystals, exhibit a periodic crystal structure , but this is usually imperfect. Several types of defects are often characterized: point defects, line defects, planar defects, bulk defects. Topological homotopy establishes

136-413: Is expressed in terms of a Burgers vector (b). For an edge type, b is perpendicular to the dislocation line, whereas in the cases of the screw type it is parallel. In metallic materials, b is aligned with close-packed crystallographic directions and its magnitude is equivalent to one interatomic spacing. Dislocations can move if the atoms from one of the surrounding planes break their bonds and rebond with

153-418: The edge dislocation and the screw dislocation. "Mixed" dislocations, combining aspects of both types, are also common. Edge dislocations are caused by the termination of a plane of atoms in the middle of a crystal. In such a case, the adjacent planes are not straight, but instead bend around the edge of the terminating plane so that the crystal structure is perfectly ordered on either side. The analogy with

170-415: The arrangement of atoms in matter, particularly when that arrangement has regular features. A steady increase in the number of submitted papers led to the journal being split into Section A , covering fundamental and theoretical studies, and Section B , dedicated to reports of structures, in 1968, together with a new journal, the Journal of Applied Crystallography . In 1983, Section C , devoted to

187-437: The atoms at the terminating edge. It is the presence of dislocations and their ability to readily move (and interact) under the influence of stresses induced by external loads that leads to the characteristic malleability of metallic materials. Dislocations can be observed using transmission electron microscopy , field ion microscopy and atom probe techniques. Deep-level transient spectroscopy has been used for studying

SECTION 10

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204-407: The crystal structures of small molecules, was added, with Section B now focusing on biological, chemical, mineralogical and metallurgical crystallography. The rapid expansion in biological crystallography led to the launch of Section D in 1993. The journals launched online versions in 1999, and in 2000 the journals began to provide electronic article submission and subscription access online. This

221-637: The crystallographic methods that are used to study crystalline and non-crystalline matter with neutrons , X-rays and electrons , their application in condensed matter research, materials science and the life sciences , and their use in identifying phase transformations and structural changes of defects , structure-property relationships, interfaces and surfaces etc. The journal also covers developments in crystallographic instrumentation and apparatus, theory and interpretation and numerical analysis and other related subjects, together with information on crystallographic computer programs. The journal

238-406: The electrical activity of dislocations in semiconductors, mainly silicon . Disclinations are line defects corresponding to "adding" or "subtracting" an angle around a line. Basically, this means that if you track the crystal orientation around the line defect, you get a rotation. Usually, they were thought to play a role only in liquid crystals, but recent developments suggest that they might have

255-405: Was P. P. Ewald , who wrote in the preface to the first issue Acta Crystallographica is intended to offer a central place for publication and discussion of all research in this vast and ever-expanding field. It borders, naturally, on pure physics, chemistry, biology, mineralogy, technology and also on mathematics, but is distinguished by being concerned with the methods and results of investigating

272-499: Was established in conjunction with the foundation of the International Union of Crystallography in 1948. Both were established to maintain an international forum for crystallography after the Second World War had led to a loss of international subscription to, and the eventual nine-year closure of, the main pre-war crystallography journal, Zeitschrift für Kristallographie . The founding editor of Acta Crystallographica

289-496: Was followed by the launch of an online-only journal, Section E , for brief reports of new small-molecule structures, in 2001; this journal became fully open access in 2008. A second online-only journal, Section F , dedicated to short reports of macromolecular structures and reports on their crystallization, followed in 2005. The IUCr moved to online-only publication for all its journals from 2014. Journal of Applied Crystallography The Journal of Applied Crystallography

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