Most ductile element

Gold (Au) and lead (Pb) are the most ductile elements, with a calculated ductility index D equal to 0.93 – where the values of D of 1 and 0 are those for perfect ductility and no ductility. Ductility is the ability that a solid material has to deform in all three dimensions under tensile stress, without failure or rupture. An example of a material with very high ductility is a gold sheet, which can be stressed to form a very think gold lamina (gold leaf) without breaking. The ductility index of gold and lead was calculated using the measured Poisson’s ratio (named after 19th-century French scientist Siméon Poisson), which indicates how thin a material becomes when it is squashed, or pulled at both ends. The higher Poisson´s ratio, the higher the ductility of the elements. Lead and gold both have a Poisson´s ratio of 0.44 (the maximum value being 0.5). The ductility index was determined considering theoretical modelling, which correlated the Poisson ratio to the atomic structure of pure solid elements. This record was confirmed on 21 October 2012 by Richard M. Christensen and Kurt M. Christensen, who made the correlation between Poisson’s ratio and the element structure.