May 17, 2017
News Release

Self-assembly Forces in Crystals

20170517102800882

As particles move around in solution, ions drive them to approach each other. The same ion-induced forces adjust the particles so their faces are arranged as an ideal crystal. Then solvent leaves the gap between the particles, and a defect-free crystal is formed.

Rocks, shells, bones — they're all made of crystals that grow from smaller crystals that attach to each other. A better understanding of how small crystals join themselves together might improve energy storage and other applications that rely on crystallization.

Two researchers at the Department of Energy's Pacific Northwest National Laboratory used a computer model to study self-assembly in a titanium oxide mineral called anatase. Maria Sushko and Kevin Rosso designed a model that re-created the conditions in which the smaller crystals grow. Then they measured the attraction and repulsion between simulated nanocrystals to dig out the forces responsible for crystal self-assembly, publishing in the journal Nanoscale.

Based on their simulations, the researchers described how the anatase nanocrystals self-assemble: As two nanocrystals float near each other, ions within the liquid environment drive them towards each other. At the same time, water between them prevents them from immediately slamming into each other. Wavering there between attraction and repulsion, the nanocrystals make slight adjustments in their positions. When almost or perfectly aligned, and after attractive forces win out and allow the crystals to touch, chemical forces take over and the nanocrystals fuse together.

Read more in this research highlight.

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