Compression Causes Expansion

Poisson Effect Driven Anomalous Lattice Expansion in Metal Nanoshells

Research team: Ganesh Iyer, Suboohi Shervani, Gargi Mishra, Deb De, Arun Kumar, Sri Sivakumar, Kantesh Balani, Raj Pala and Anandh Subramaniam

Surface tension compresses a water droplet and equivalently the effect of surface stress is to decrease the lattice parameter in metal particles. The effect of surface stress and elastic properties like Poisson's ratio can be accentuated in lower dimensional systems like metal nanoparticles. The I.I.T. Kanpur team, using a two scale computational method and transmission electron microscopy, not only show a lattice expansion due to purely surface stress effects in a metallic system, but also discover anomalous lattice expansion in the case of very thin walled in metal nanoshells. This effect where "compression is causing expansion" has been hitherto unanticipated. The Kanpur team not only establish that this is a Poisson effect driven phenomenon and but generalize it all metal nanoshells.

Reference

"Poisson effect driven anomalous lattice expansion in metal nanoshells"
Ganesh Iyer, Suboohi Shervani, Gargi Mishra, Deb De, Arun Kumar, Sri Sivakumar, Kantesh Balani, Raj Pala and Anandh Subramaniam,

Applied Physics Letters 110, p.131603, 2017.