Collaborative Research: Design of Low-Hysteresis High-Susceptibility Materials by Nanodomain Engineering

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NONTECHICAL SUMMARYThis award supports theoretical and computational research aimed to develop new design concepts and principles for shape memory alloys, and ferroelectric and ferromagnetic materials to achieve improved functionality for various applications. In these materials structural domains can switch from one to another by the application of an external field, such as stress, electric or magnetic fields, allowing sensing and actuation to be realized simultaneously. These smart materials have found critical applications in many fields, including medical devices, satellites, robots, navigation systems, data storage and retrieving, electromechanical and electro-optic systems, to name a few. However, typical domain structures formed in these materials are too large leading to properties that are not optimal for applications. Another common problem is that functional fatigue that leads to premature failure. The PIs will use advanced computational and theoretical methods to investigate new design concepts and principles that connect crystal structure, defects, domain structure and functional properties. These design concepts and principles are aimed to guide experimental efforts and accelerate the discovery of new smart as well as structural materials with optimal properties. This is in alignment with the Materials Genome Initiative. This project will directly prepare graduate students to immediately contribute to the success of integrated computational materials science and engineering. Additionally, the training of researchers involved in materials development will afford a rapid uptake of new design concepts and methodology, resulting in increased effectiveness of materials technologists. The educational outreach of the project is designed to have a significant influence on encouraging high school students with diverse ethnic backgrounds to enter science and engineering disciplines.TECHNICAL SUMMARYThis award supports theoretical and computational research that focuses on ferroic-based functional materials including shape memory alloys, and ferroelectric and ferromagnetic materials. The main objective of this project is to accelerate the discovery of novel low-hysteresis high-susceptibility ferroic-based functional materials with strong fatigue resistance via the design of (a) transformation pathway networks, and (b) structural and chemical heterogeneities. The former explores the means to achieve high susceptibility by identifying systems with isolated circular transformation pathways, while the latter explores how to transform conventional micron-sized, long-range ordered, self-accommodating strain, polarization and magnetization domains into nanodomains by suppressing autocatalysis and regulating the spatial extent of domain growth and coarsening during ferroic phase transitions. A rigorous theoretical framework will be developed based on group theory, phase transformation crystallography and graph methods to analyze transformation pathway networks (TPNs). Through investigating the symmetry and topology of TPN graphs, a new classification of structural phase transformations will be introduced. The PIs aim to distinguish three distinct TPN types: ones that could provide high susceptibility, ones that are reversible and exhibit shape memory effect, and ones that could generate dislocations through transformations causing functional fatigue. The PI will perform systematic first principles and atomistic calculations for specific systems to assist in constructing and classifying TPN graphs, to quantify the energy landscapes, and to investigate the effects of various crystalline defects. Finally phase field simulations will be carried out to examine possible continuous phase separations and other mechanisms to generate nanoscale structural and chemical non-uniformities in the parent phase and to study their effects on subsequent ferroic phase transitions and ferroic nanodomain formation. The responses of these ferroic nanodomains to temperature and external fields will be documented. Drastically different properties from those of their microdomain counterparts are expected, in particular ultra-low-modulus quasi-linear pseudoelasticity, low hysteresis, high susceptibility such as giant piezoelectricity, giant magnetostriction and giant non-hysteretic strain response, and strong fatigue resistance.