Properties and Applications of Nanocrystalline Alloys from Amorphous Precursors

Abstract

Systems with negative Poisson ratio (NPR) behave in a counterintuitive way: when pulled (pushed) in one direction, they expand (shrink) in all directions. In this lecture we discuss application of computer simulations to study NPR systems and sketch an idea — based on the Cauchy relations — of systematic studies of mechanisms which may lead to NPR. Roughly speaking, the NPR systems can be divided into three groups: (i) systems of artificial structures (on micro-, mezo- or macroscopic scale), (ii) systems at special conditions ( e.g. systems at negative pressure, systems near some phase transitions, etc.), and (iii) thermodynamically stable phases. We concentrate on the third group and study a class of two-dimensional model particles forming isotropic solid phases which exhibit the NPR. Depending on the interaction potential used, they show periodic or periodic structures. The Poisson ratio of the periodic solids can be decreased by transforming them into periodic crystals.