Aerospace and Mechanical Engineering
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AEM Research Discovers New Information on Entropically Stabilized Dislocations

Professor Ellad B. Tadmor and former postdoctoral fellow Dr. Woo Kyun Kim's paper on "Entropically Stabilized Dislocations" is the first explicit demonstration of a dislocation that is stabilized solely due to entropy without a corresponding potential energy well.

Dislocations are local misarrangements along a line in the pattern of atoms that is otherwise crystalline and perfect. Permanent deformation in metals and other crystals occurs as a result of the motion of these defects, each of which carries with it a quantum of plastic or irreversible deformation. Dislocations also affect the thermal, chemical and electrical properties of crystals.

"Dislocations play a very important, and often destructive, role in electrical an optical materials, and they are responsible for the plasticity of metals; thereby making them of critical importance," explains AEM Professor Tadmor. "Our paper highlights the discovery of something fundamentally new about the nature of dislocations, unknown since their discovery exactly 80 years ago."

For the first time, Tadmor and Kim show the possibility of "Entropically Stabilized Dislocations" (ESD) that exist due to entropic effects without a corresponding energy well. Using simulations and theoretical modeling, the AEM team established that partial dislocations can form even when it is energetically unfavorable, purely due to entropic effects. This means some dislocations exist simply because they increase the disorder in the universe.

The existence of ESDs would have profound consequences, as many scientists have long tried to explain the behavior of dislocations and the patterns that they form purely based on their energies. The possibility that some of these patterns are stabilized by entropy or disorder opens up new horizons in the understanding of crystalline materials.

For more information, please contact Professor Tadmor at tadmor@umn.edu or (612) 625-6642. Additionally, an article describing the new discovery about the nature of dislocations, the most important defects in crystalline materials, will appear in the prestigious Physical Review Letters journal.

A figure of a moving dislocation from Professor Tadmor's book.
(E. B. Tadmor and R. E. Miller, "Modeling Materials: Continuum, Atomistic and Multiscale Techniques," Cambridge University Press, 2011.)


Last Modified: 2014-02-13 at 13:25:40 -- this is in International Standard Date and Time Notation