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Atomic physics and the strength of metals
| Content Provider | Semantic Scholar |
|---|---|
| Author | Nkrumah, Kwame |
| Copyright Year | 2017 |
| Abstract | In the previous Rutherford lecture Sir Lawrence Bragg (1961) gave an account of the history and present position of crystallography. Crystallography consists of the study of the regular ways in which atoms or molecules are arranged in solids, and crystallographers now investigate substances of ever-growing complexity. At the same time, alongside crystallography, there has grown up a science which is related to it, namely, a study of the ways in which these regular arrangements can break down. If there are many thousands of crystal structures known in nature, you would guess that there must be tens of thousands of possible defects; this may be so, but in fact the study of defects is confined at the present time to those which are observed in the simpler crystal structures, in metals, oxides and so on, and so we are far from knowing the full complexity that may exist. Actually, however, there is one form of defect which has a certain simplicity and very great theoretical and practical importance, namely, the dislocation. I t is the history and present status of this concept that form the subject matter of this lecture. There is a certain appropriateness in the dislocation as a subject for a Ruther ford lecture. I t is not only that one of the most important papers on the subject (G. I. Taylor 1934) came from Rutherford’s Cavendish, or that the first photo graphs of moving dislocations were obtained in the same laboratory (and indeed in a room that he formerly used) 25 years later by P. B. Hirsch and his colleagues. I t is also because of the similarities and differences between a dislocation and a particle. Rutherford was a man of particle physics; his a-particle, moving up to and repelled by the atomic nucleus, making itself visible by a flash on a zinc sul phide screen or by a track in an expansion chamber, is the most obviously particle like of particles. Atomic physics was built on the concept of particles with forces between them. A dislocation is not a particle; it is a line. Nevertheless, like a particle in atomic physics, it can move about and be attracted or repelled by other dislocations or by impurities or point defects in the material. I t is, as far as I |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://rspa.royalsocietypublishing.org/content/royprsa/275/1361/149.full.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Adobe Flash Cell Nucleus Crystal structure Crystallography Dislocations Graph - visual representation Metals Norm (social) Oxides Paper Particle Software bug Subject matter expert Turing test Transcutaneous Electric Nerve Stimulation solid substance |
| Content Type | Text |
| Resource Type | Article |
