Structure of Metals

Abstract

THIS note describes some rather unexpected facts observed when nickel and gold are investigated at high dispersion with X-rays. In these experiments the distance between the film and the specimen is either 20 cm. or 30 cm. The primary X-rays after passing through a pin-hole of about ½ mm. diameter reach the specimen, a flat disk of approximately 1–1·5 sq. cm. surface, and are scattered back to the photographic film. The β₁ line of iron (wave-length 1.75301 A.) gives with the (400) crystal plane of nickel a glancing angle of 85½° at room temperature. A lattice change of 1/1,000 produces a shift of more than 7 mm. of the line on the film, and since the position of a sharply defined line can easily be measured to 1/10 of a millimeter, lattice changes of the order of 10^-5 are observable. No such reflexions are ever obtained when the material is examined in bulk even with the purest and most carefully annealed substances. This is well known. With annealed powders or filings it is different, as is shown for example in the investigation of Owen and Yates¹ on pure nickel.