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Published on: March 13, 2016
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Relevance of packing to colloidal self-assembly
Rose K Cersonsky1, Greg van Anders2,3, Paul M Dodd2
1Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, MI 48109.
Summary
Packing arguments do not explain colloidal crystal structures, even for densest packing. Imperfect particle shapes are optimal for hard particle colloidal crystals at any pressure.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Colloidal Science
Background:
- Packing arguments have historically rationalized crystal structures since the 1920s.
- These arguments are increasingly applied to complex nanoparticle and colloidal crystal structures, with variable success.
Purpose of the Study:
- To investigate the causal role of packing mechanisms in hard particle models of colloidal crystals.
- To determine the conditions under which packing arguments accurately predict crystal structures.
Main Methods:
- Analysis of three crystal structures using their ideal packing shapes.
- Examination of hard particle approximations in colloidal crystal formation.
Main Results:
- Packing is not the ordering mechanism, even when the self-assembled structure matches the densest packing.
- The optimal particle shapes for hard particle colloidal crystals at finite pressures are not perfect ideal packing shapes.
Conclusions:
- Packing arguments alone are insufficient to explain the formation of all colloidal crystal structures.
- Deviations from ideal shapes are crucial for achieving stable colloidal crystals under pressure.
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