PULGON: Phonons Understood via Line Groups Of Nanomaterials

By precisely controlling the position of atoms, an almost infinite variety of structures can be imagined with sizes below one tenth of one thousandth of a millimeter. Such nanostructures are found everywhere in nature. For instance, long filaments with very small diameters provide structure and shape to our own cells, making transport of components inside those same cells possible, and allow many microorganisms to move. Similar kinds of thin but long nanostructures can be artificially created and have the power to enable revolutionary technological progress in the form of more resistant materials, better water filters or smaller, faster electronic components. To be able to fulfill that potential, however, tools are necessary that can calculate the properties of those structures from basic physics and guide nanoengineering efforts. The mixture of long and short dimensions in the structures described above poses a problem for many of the items in the toolbox of computational materials science, which are best adapted to work with systems that are either big or small along all directions of space. Case-by-case solutions to those limitations exist, but they involve hard compromises in terms of computing time and introduce unrealistic artifacts in the results. This project will create a software framework to study tube- and wire-like nanostructures using a specific method, and use that framework to study how heat spreds in those structures. This aspect of their behavior has been chosen because working temperatures and how easily heat can be removed greatly affect the performance and reliability of these nanowires and nanotubes when used in electronics and energy harvesting applications. The guiding thread of the treatment will be symmetry, i.e., repeating geometric patterns in these large systems that allow studying them by looking at a small, ever-repeated building block. Step by step, more complex structures will be tackled, starting from simple nanowires made of a single element and later introducing defects, interfaces and other sources of disorder. The knowledge gained from this study will provide a more solid foundation for designing task-specific nanowires and nanotubes at the atomistic level. Moreover, the underlying framework will be released to the community as open- source software and is expected to find applications in the study of nanosystems well beyond heat transport.