Poisson Ratios of Polycrystals

Abstract

Poisson ratios of fee and bcc polycrystals are calculated for a variety of atomic models and the theoretical results are compared with experiment. In contrast with previously reported results, it is found that an accurate description of polycrystalline Poisson ratios of metals is obtained from the model in which the binding energy Ebind consists of a structure dependent part Estr and a volume dependent part Evol. Investigations are made of the general, inherent abilities of various subsets of this model to describe experimental polycrystalline Poisson ratios; these subsets include the Cauchy model (i.e. Evol is neglected in Ebind) and the Milstein-Rasky model (i.e. the volume dependent contribution to the bulk modulus χvol is neglected). In addition, specific com putations of polycrystalline Poisson ratios are made for the complete families of bcc and fcc Morse function (Cauchy) crystals and for (non-Cauchy) models (simplified forms of which are suggested by pseudopotential theory for the noble metals).