Perfect crystals are elastic. When a stress is applied and then removed the crystal will bounce back to its original shape. However, in reality no crystal is perfect. If the applied stress is too large the crystal will fracture. Understanding fracture is a big deal in materials science and involves some fascinating physics, including the role of topological defects.
There are two distinct properties: elasticity and plasticity. They are associated with temporary and permanent changes in shape in response to an applied stress.
They are quantified by the elastic stiffness and the tensile strength, respectively. They reflect material properties at quite different length scales.
A beautiful and accessible short introduction is
Bart Kahr & Michael D. Ward
This is a commentary of some work by a few of my UQ chemistry colleagues, who have made and studied a molecular crystal that is incredibly flexible, as seen in this movie.
Anna Worthy, Arnaud Grosjean, Michael C. Pfrunder, Yanan Xu, Cheng Yan, Grant Edwards, Jack K. Clegg & John C. McMurtrie
A particular advance is that they use a synchrotron to perform spatially resolved X-ray crystallography to determine how the crystal structure varies spatially within a bent crystal.
The material of interest has quasi-one-dimensional antiferromagnetic interactions and has been studied theoretically by my condensed matter theory colleagues.
Elise P. Kenny, Anthony C. Jacko, Ben J. Powell
But there is more...
A recent Science paper describes ice fibers that were particularly flexible.
Peizhen Xu, Bowen Cui, Yeqiang Bu, Hongtao Wang, Xin Guo, Pan Wang, Y. Ron Shen, Limin Tong
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