Structure and Function of Heteroanionic Materials

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NONTECHNICAL SUMMARYTwenty-first century microelectronic and battery technologies rely on components consisting of transition metal oxides that can accommodate reversible changes in the distribution of their electrons. This award supports theoretical and computational research on the fundamental science of heteroanionic materials, which are compounds consisting of more than one anion beyond oxygen such as oxynitrides, oxyfluorides, and oxysulfides. These compounds benefit from the stability of oxide materials, but have the added advantage of tunable electronic, magnetic, and topological properties owing to the additional secondary anion, which allows for greater control over the electron distribution.The project goals are to design, discover, and control the properties of heteroanionic materials displaying ferroelectricity, metal-insulator transitions, and topological band structures by establishing links between crystal structure and anion chemistry, profiting from a coupling of theory, simulation, and comprehensive experimentation. The project utilizes quantum-mechanical based calculations to establish model frameworks and knowledge that are both descriptive and predictive. These models and approaches may be expanded to materials beyond heteroanionic materials, enabling an unprecedented expansion of compounds with varying electronic functions for future technologies.The teaching and training of students and the discovery capabilities of the project are also interwoven and aimed at broadening participation of underrepresented students in Science Technology Engineering and Mathematics disciplines through public outreach events, through undergraduate and graduate curriculum development, and by involving students with experiential and interdisciplinary training. The educational impact extends to high-school students by developing materials physics/engineering modules that meet Next Generation Science Standards in concert with high school teachers.TECHNICAL SUMMARYComplex transition metal oxides are utilized in a variety of technologies owing to their properties ranging from ferroelectricity to high-temperature superconductivity supported by polarizable oxide anions. The design, discovery, and control of new transition metal compounds, particularly those with multiple anions (heteroanionic materials) rather than multiple cations (homoanionic oxides with a single anion), with novel properties and superior performance are crucial to the continued development of present and future technologies. This award supports theoretical and computational research on the fundamental science of heteroanionic materials such as oxynitrides, oxyfluorides, and oxysulfides.The project goals are to implement and extend a heteroanionic materials design scheme for understanding the complex interplay among atomic structure, anion order, and band structure on novel electronic and quantum states and to advance new heteroanionic materials exhibiting superior functionalities and/or responses not found in homoanionic materials. The project utilizes a computational strategy, which integrates group theoretical techniques, derivative-structure tools, and density functional theory, to understand the electronic and optical properties of oxynitrides, oxyfluorides, and oxysulfides within three thrusts focused on (i) geometric and chemical control of noncentrosymmetry for acentric function; (ii) probing metal-insulator transition mechanisms for materials discovery; and (iii) novel routes to anion-ordered topological semimetals. The project will deliver new knowledge to facilitate the selection and design of materials with tunable electronic states derived from multiple anions. It benefits society by advancing the repertoire of structure-based design strategies to control electronic properties, which could lead to discovery of reconfigurable materials for low-power and brain-inspired microelectronics, transparent optoelectronics, and quantum information systems. In addition, educational goals of the project include the teaching and training of students at multiple levels and broadening STEM participation by underrepresented students. These goals extend to high-school students by developing materials physics/engineering modules in concert with high school teachers that meet Next Generation Science Standards. These efforts will impact the next-generation workforce by endowing students and teachers problem-solving skills to be success in globally competitive careers.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.