Nanoparticle Simulations

TiO₂ is naturally available in three different polymorphs, namely, anatase, rutile and brookite. Rutile is found to be the most stable phase in bulk, with anatase and brookite transforming to rutile irreversibly. But at the nanoscale, anatase was experimentally found to be the most stable polymorph. To further understand the physical characteristics of nano-titania is the major goal of our research efforts and to fulfill this goal we are using molecular dynamics simulations as a tool.

Sintering of particles has been studied for many decades, but very little is known about sintering of particles whose dimensions are only a few nanometers. Are the mathematical models and assumptions, which are applicable for larger sintering particles also valid for nanoparticles? If not, how can one predict the temperature variation or phase transformation involved (if any) during nanoparticle sintering? These are few of the questions that we plan to answer with our research on TiO₂ nanoparticles.

Nanoparticles in vacuum behave much different than the nanoparticles in aqueous medium. We have found that TiO₂ nanoparticles are actually more crystalline when immersed in water and the presence of water may affect the phase transformations and the process of nanoparticle sintering.

It has been suggested that one of the mechanisms by which anatase transforms to rutile is via brookite. We have studied phase transformations occuring during nanoparticle sintering using MD simulations and our interesting finds have been recently published in ACS Nano.