Chemical Physics seminar: Kinetic Pathways to Control Nanocrystal Shapes

Seminar given by Dr. Carlos L. Bassini, Institute for Multiscale Simulation, Department of Chemical and Bioengineering, FAU Erlangen-Nürnberg, Germany

Dr. Bassini's research centers on modeling and simulating multiscale interactions in crystal formation from solution.

The shape of nanocrystals is crucial in determining surface area, reactivity, optical properties, and self-assembly behavior. The current theory on shape formation is based on thermodynamic equilibrium and predicts that each crystal structure should enforce a unique shape, with few morphological variations depending on solution chemistry. Whereas this theory succeeded in explaining crystal habits in mineralogy, it mispredicts many nanocrystals, pointing out the necessity of a non-equilibrium description of shapes. In this talk, I show robust and scalable kinetic Monte Carlo simulations that capture kinetic effects of ligands and ions in solution at the molecular scale, while enabling the formation of facets and shapes at mesoscopic scales. This method is suitable to answer long-standing questions on kinetic traps, symmetry-breaking, and bifurcation of growth pathways leading to shape polydispersity. I show that even simple fcc crystals modeled through Lennard-Jones interactions span diverse shapes when submitted to non-equilibrium. I discuss the growth mechanism for the shape families of symmetry-preserving polyhedra (cubes, octahedra, rhombic dodecahedra, and their truncations), symmetry-breaking by stacking faults (tetrahedra, triangular and hexagonal plates, prismatic rods), and multiply twinned nanoparticles (decahedra, icosahedra, penta-twinned rods). Finally, I will hint at an extension to practice on heterostructured core-shell noble metal nanoparticles and self-assembled colloidal crystals of metal-organic frameworks.