Science and Engineering

Lehigh University

Martin P. Harmer, Elizabeth A. Holm, Gregory S. Rohrer
Bethlehem, PA
December 2015

The atoms in the solids that we interact with in the material world typically move exponentially faster with increasing temperature, obeying a classical law of physics called the Arrhenius equation.  Such thermally activated motion fundamentally limits the properties and performance of materials.  A grand challenge in condensed matter science is to combat or ideally reverse this trend.  Examples of counter Arrhenius (anti-thermal) behavior exist, some previously observed by these investigators, in which atoms actually move slower when they get hotter and faster when they get colder, reversing what is normally expected in nature.  We know anti-thermal behavior involves only a sub-set of atoms located between internal grains (grain boundaries).  This team, which includes collaborators at Carnegie Mellon University, will pursue the atomic mechanisms for these anti-thermal processes by combining atomistic simulations of the temperature dependence of grain boundary velocities for a vast number of possible boundary types, with a new experimental approach for isolating and measuring the independent velocities of individual boundary types simultaneously and in-situ hot-stage atomic resolution microscopy.  They aim to uncover the mechanism of anti-thermal behavior and to identify the boundary characteristics that exhibit the strongest anti-thermal behavior, guiding the purposeful design of new materials with enhanced thermal performance.

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