Elastic Constants of Galena

Abstract

RECENTLY, Ramachandran and Wooster¹ have obtained the elastic constants of galena, among other substances, from measurements on diffuse reflexion of X-rays, and reported disagreement with the values given earlier by one of us². Ramachandran has also directed our attention to this in private communications. This substance, in the light of such values, also figures as an exception in a paper by Lonsdale³ dealing with the vibration amplitudes of atoms in cubic crystals. Its elastic constants have therefore been re-determined, employing the wedge method and a very much better crystal than was available at the time of the earlier investigations. Frequencies in the range 2–12 Mc./sec., and (001) and (111) sections of different thicknesses ranging from 1.450 mm. to 1.929 mm., have been used. Constants now obtained along with the bulk modulus K in units of 10¹¹ dynes cm.⁻² are c₁₁ = 12.70, c₁₂ = 2.98, c₄₄ = 2.48 and K = 6.22. They show that the Cauchy relation is fairly well satisfied. c₄₄ and c₁₂ do not differ very much from those of Ramachandran and Wooster, whereas c₁₁ is somewhat larger. These values are to be regarded as much more reliable than any published earlier.