DMREF: Collaborative Research: Complex Nanofeatures in Crystals: Theory and Experiment Meet in the Cloud

Non-technical Description: Everything, from phones to people, are made of materials. As mankind seeks technological solutions to its biggest problems, we constantly seek materials that will do their tasks with higher performance. We want batteries with higher energy density, screens that are touch sensitive, windows that are smart, and so on. Inevitably, the search for better materials leads to greater complexity in the materials themselves, including nanostructuring them: engineering them on a tiny scale of one billionth of a meter. Recent investigations have shone light on a previously overlooked class of materials: bulk crystals that naturally have nanoscale broken symmetry structures patterned over the average crystal structure. These were overlooked because they are hard to detect experimentally, something which recent developments in experimental techniques is overcoming. Since they weren't known about, there was no theoretical effort to find and understand them. However, recently theoretical support for their existence has come through the discovery that such nanostructured symmetry broken structures may, in some cases, be energetically more stable than the undistorted parent structure. Such materials are being referred to as polymorphous network materials (PNMs). The goal of this Designing Materials to Revolutionize and Engineer our Future (DMREF) project is to understand the origin of this mysterious materials complexity and with the greater understanding, to discover new PNMs. (Often nature prefers simpler, high symmetry solutions to its problems. Why is it not the case in these PNM materials?) The classes of material that are known PNMs are transition metal oxides, halides and chalcogenides. These are among the most interesting materials scientifically (exhibiting exotic but poorly understood effects such as the ability to turn from a metal to an insulator as a function of temperature or field, high temperature superconductivity and colossal responses to applied fields) and with many potential technological applications. This project will combine the theory and the experimental developments with cloud-based computational infrastructure that will allow a broader range of researchers to search for novel PNMs, and to understand the existing ones better. A key aspect of this project will involve the training of the next generation of scientists and engineers in the use of the Pair Distribution Function methodology in the cloud platform. The PIs will educate US and African graduate students in the interdisciplinary research philosophy integral to the Materials Genome Initiative.

Technical Description: The project will combine computation to predict, synthesis to make, and x-ray and neutron local structure characterization to validate the predictions, an approach that embodies the Materials Genomics philosophy and applies it to PNMs. Quantum mechanical density functional theory (DFT) calculations will be applied to supercells of transition metal oxides and chalcogenides that are sufficiently large to support the PNM effect, to see if nanostructured distortions can lower the total energy. These will be applied to classes of known materials, such as hybrid organic-inorganic halides, to search for and characterize the nature of the PNM distortions. The most promising materials will be synthesized and characterized using PDF, a diffraction method sensitive to the local distortions. A computational infrastructure will be built that will save results, both theoretical and experimental, to databases for later mining. The infrastructure will be made available to the community to carry out their own computational 'experiments'.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.