Argonne National Laboratory Center for Nanoscale Materials U.S. Department of Energy

Understanding Nanocrystal Shapes through Simulation

A. Barnard

Anatase NanocrystalsNanoparticles of various materials have been found to possess a number of remarkable properties that depend upon their finite size. In many cases however, these desirable properties may also be a function of the morphology of the nanoparticle. Experimental evidence suggests that the shape of nanomaterials is affected by such factors as size, temperature, pressure, and the chemical environment. Observations of this type invite the question: Can the shape of nanoparticles be controlled, or do thermodynamic processes rule at the nanoscale?

Researchers at the Virtual Fab Lab are using theoretical models and high-performance computing to investigate the physical principles responsible for the shape of nanocrystals and ways in which they may be manipulated. Calculations involving isolated nanoparticles (even small structures such as the anatase nanocrystals shown here) can be very computationally intensive, especially when trying to simulate the effects of particles in solution. It may also be difficult to determine whether the results of such calculations are archetypal or are representative only of the particular prototype structure. By developing a new theory for the phase stability of nanomaterials as a function of size and shape, we can eliminate much of this ambiguity. Ab initio computational methods are used to obtain a set of key parameters for the model that may then be used to examine how shape affects processes such as phase transitions. Alternatively, the model may be used to determine the experimental conditions necessary to achieve a particular shape that may be required for a specific application.

February 25, 2004

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