Heterostructure morphology stability maps in multiphase nanoparticles
In the rapidly growing field of nanocombinatorics, the advent of megalibraries of multiphase nanoparticles (NPs) has created a need for predictive computational approaches. A notable characteristic of multiphase NPs is the internal interface architecture that arises from the joining of constituent phases at boundaries. We propose a strategy to predict the ground-state interface architecture from the DFT-calculated surface and interfacial energies of all constituent phases as input and use this strategy to create stability maps to predict multiphase NP morphologies. A Potts model, a $q$-state generalization of the Ising model, in which $q-1$ spins represent discretized regions of a constituent phase, provides a flexible, discretized representation of a $(q-1)$-phase nanoparticle with arbitrary interfacial join morphology. Interactions between spins represent interactions between phases, or interfacial energies. To model the surface of a nanoparticle, an additional spin represents the surrounding environment and interaction energies with this spin are surface energies. We apply a Monte Carlo algorithm to search for the lowest-energy spin configuration. The trade-off between surface and interfacial energy minimization drives the formation of an interface morphology. We calculate a biphase nanoparticle interface morphology stability map to study the relation between the three biphase morphologies we found. Next, we use the stability map to predict NP morphologies of sample biphase systems and compare these to experimentally available data. We repeat the grid search approach for triphase nanoparticle interface morphologies and discover 11 triphase morphologies, nine more than previously enumerated. We then predict sample triphase systems and finally revisit experimentally reported triphase morphologies.