Macroscale contraction in AgGaTe⌄2 (IMAGE)
Caption
Macroscale contraction: In the undistorted large scale AgGaTe⌄2 crystal (left), a single silver atom (gray) sits at the center of each tetrahedral cavity. Upon heating, as the off-centering shifts of silver atoms within adjacent tetrahedra become correlated, the resulting rotation causes the whole macroscopic crystal to shrink in one direction (large black arrows) while expanding in another (not shown). These distortions scatter vibrations that propagate heat through the material, giving it the low thermal conductivity that makes it a promising thermoelectric material.
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Brookhaven National Laboratory
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