Negative Poisson’s ratios in metal nanoplates

• Published in: Nature communications 2014-02, Vol.5 (1), p.3255-3255, Article 3255
• Main Authors: Ho, Duc Tam, Park, Soon-Dong, Kwon, Soon-Yong, Park, Kibog, Kim, Sung Youb
• Format: Article
• Language: English
• Subjects: 639/301/1034; 639/301/357; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms4255

The Poisson’s ratio is a fundamental measure of the elastic-deformation behaviour of materials. Although negative Poisson’s ratios are theoretically possible, they were believed to be rare in nature. In particular, while some studies have focused on finding or producing materials with a negative Poisson’s ratio in bulk form, there has been no such study for nanoscale materials. Here we provide numerical and theoretical evidence that negative Poisson’s ratios are found in several nanoscale metal plates under finite strains. Furthermore, under the same conditions of crystal orientation and loading direction, materials with a positive Poisson’s ratio in bulk form can display a negative Poisson’s ratio when the material’s thickness approaches the nanometer scale. We show that this behaviour originates from a unique surface effect that induces a finite compressive stress inside the nanoplates, and from a phase transformation that causes the Poisson’s ratio to depend strongly on the amount of stretch. Materials with a negative Poisson’s ratio are rare and have been observed in bulk materials. Here, the authors report that a negative value can be seen in nanoscale metal plates under a finite stress, caused by a surface effect and a phase transformation.