  Mechanochemistry is becoming an established method for the sustainable,
solid-phase synthesis of scores of nano-materials and molecules, ranging from
active pharmaceutical ingredients to materials for cleantech. Yet we are still
lacking a good model to rationalize experimental observations and develop a
mechanistic understanding of the factors at play during mechanically assisted,
solid-phase nanoparticle synthesis. We propose herein a
structural-phase-field-crystal (XPFC) model with a ballistic driving force to
describe such a process, with the specific example of the growth of gold
nanoparticles in a two component mixture. The reaction path is described in the
context of free energy landscape of the model, and dynamical simulations are
performed based on phenomenological model parameters closely corresponding to
the experimental conditions, so as to draw conclusions on nanoparticle growth
dynamics. It is shown that the ballistic term lowers the activation energy
barrier of reaction, enabling the reaction in a temperature regime compatible
with experimental observations. The model also explains the mechanism of
precipitated grain size reduction that is consistent with experimental
observations. Our simulation results afford novel mechanistic insights into
mechanosynthesis with implications for nanaparticle production and beyond.
