Computational Modeling of Nanocrystal Superlattices

Nanocrystal superlattices (NCSLs) are materials formed by assembly of monodisperse nanocrystal building blocks that are tunable in composition, size, shape, and surface functionalization. Such materials offer the potential to realize unprecedented combinations of physical properties, however, theoretical prediction of such properties remains a challenge. Because of the different length scales involved in these structures, modeling techniques at different scales, from ab-initio methods up to continuum models, can be used to study their behavior. This presents a challenge of understanding when and for which properties we can use computationally inexpensive continuum or mesoscopic models and when we will have to use microscopic models. Our goal here is to develop models that can predict phononic and thermal properties of different NCSLs. This includes (1) predicting bulk mechanical properties of NCSLs such as Young's and bulk modulus which are related to the behavior of low frequency acoustic phonons (2) predicting phononic band gaps through finding phonon dispersion curves of NCSL (3) predicting thermal conductivity of NCSLs. We also study the topic of one-way phononic devices that can possibly be implemented with acoustic metamaterials such as NCSLs or phononic crystals in general. This idea of one-way phonon isolation is investigated in a theoretical framework by considering systems such as acoustic waveguides and low dimensional materials.