Discovery of new self-assembled crystal structures

Nanotechnology is the study and manipulation of matter at an extremely small scale, typically at the level of individual atoms or molecules. One promising area of research within nanotechnology is self-assembly, which involves the spontaneous organization of individual building blocks into larger structures without the need for external guidance or intervention. Self-assembly is a powerful tool for creating complex and precise structures at the nanoscale, and it has potential applications in fields ranging from medicine and electronics to energy and environmental science. One specific area of self-assembly research involves the formation of self-assembled crystal structures. Self-assembled crystal structures are created when individual molecules or atoms come together in a regular and repeating pattern to form a larger, three-dimensional crystal. These crystals can have a variety of shapes and sizes, and they can be composed of a wide range of materials, including metals, semiconductors, and organic compounds. The key to creating self-assembled crystal structures is to carefully control the interactions between the individual building blocks. These interactions can be controlled by tuning factors such as temperature, solvent composition, and the presence of other molecules or ions. By carefully manipulating these factors, researchers can encourage the building blocks to come together in a specific pattern, leading to the formation of a self-assembled crystal structure. One particularly promising area of research within self-assembled crystal structures is the creation of “bottom-up” nanoelectronics. In this approach, individual electronic components such as transistors and diodes are created using self-assembly techniques, allowing for the creation of complex electronic circuits at the nanoscale. This approach has the potential to revolutionize the electronics industry by enabling the creation of smaller, faster, and more efficient devices.

Using a targeted computational approach, researchers in the Department of Materials Science and Engineering at Cornell University have found more than 20 new self-assembled crystal structures, none of which had been observed previously. The research, published in the journal ACS Nano is authored by Ph.D. student Hillary Pan and Dr. Julia Dshemuchadse, assistant professor of materials science and engineering. The authors  found new structures that weren’t previously listed in any crystal structure database; these particles are actually assembling into something that nobody had ever seen before. The team conducted a targeted search for previously unknown low-coordinated assemblies within a vast parameter space spanned by particles interacting via isotropic pair potentials, the paper states. Low-coordinated structures have anisotropic local environments, meaning that the geometries are highly directional, so it’s incredible that we’re able to see such a variety of these types of structures using purely non-directional interactions. Low particle coordination is a structural characteristic key to the functional properties of many technologically important materials including framework structures such as metal-organic frameworks, clathrates, and zeolites as well as photonic crystals such as diamond.

The researchers developed a new functional form for particle interactions in which all features can be tuned independently. By systematically changing pairs of parameters in simulation, the researchers were able to control various features of the particles’ interaction landscape. Despite limiting the search to a small region of the vast parameter space of possible particle interactions, a wealth of complexity and symmetry is apparent within these crystal structures, which include clathrates with empty cages and low-symmetry structures, which had also not been observed previously in simulation. The work demonstrates that complicated structures can develop from simple interactions and adds new theoretical structures for others working in the field. The team’s flexible and intuitive interaction potential design serves as an important step towards determining the characteristics of particle interactions that lead to certain structural properties, useful for establishing synthetic rules to make target structures. The authors’s findings suggest that there are potentially limitless new and exotic materials configurations possible through controlled self-assembly. This is the first time a study quantifies the relationship of this isotropic pair potential with the crystal structures that result. These new crystal structures can now serve as design targets for researchers who actually make nanoparticles and colloids.

Overall, self-assembled crystal structures are a fascinating area of research within nanotechnology, with potential applications across a wide range of fields. By carefully controlling the interactions between individual building blocks, researchers are able to create complex and precise structures at the nanoscale, with potential applications ranging from electronics to medicine.