CAREER: Ligand Engineering of Structure and Electronic Function in Complex Metal Oxyfluorides

Overview: The career-development plan (CDP) is a synergistic research, education, and outreach program that focuses on the design of functional electronic behavior in transition metal (TM) oxyfluorides using oxygen/fluorine substitution and ordering. Combinations of applied group theory, informatics, and ab initio density functional theory calculations will: (1) Advance new theoretical methods to establish structure-function axioms for how anion order can be used to direct crystal structure and properties. (2) Formulate a quantitative theory of structure stability based on understanding the ligand sublattice symmetry and local bonding interactions within individual polyhedral. (3) Understand the electronic consequences of the MO_{x}F_{6-x} coordination topologies, and establish control over geometry to direct orbital energies and non-linear optical behavior. (4) Implement an ensemble educational plan (EEP) to foster awareness, understanding, and appreciation of advanced technology materials and data-driven scientific methods. The EEP will build cognitive skills through an emphasis on cause/effect relationships that are axiomatic to the research objectives. Intellectual Merit: This research addresses problems in directing the structure and electronic properties of TM oxides. Conventional routes to direct the responses primarily rely on cation substitution and interfacial effects in thin films/superlattices, which offer limited control owing to a single (oxygen) anion--this makes materials discovery challenging. Remarkably, ligand (anion) engineering with TM-(O,F) polyhedral building blocks remains to be fully exploited for property control/design, especially in these materials which already find use in energy generation and storage, phosphors, and catalysis. Success in this program will produce new knowledge underlying crystal stability, chemical bonding, and electronic behavior. It will articulate predictive rules for selecting new oxyfluorides, making it transformative in accelerating discovery, enabling an unprecedented expansion of compounds with varying electronic functions. The PI has ongoing collaborations with leading experts in oxyfluoride synthesis and characterization; understanding derived here will stimulate experimental methods and vice versa. It naturally extends the PI’s line of structure-driven materials research, and builds on his expertise in combining multiple theoretical approaches, which has generated both publications and invited reviews in prestigious journals. Broader Impacts: The CDP will impact scientific discovery and the teaching and training of both students from 9-16 and high school teachers. Continued investigation of known materials, while valuable, is inadequate to formulate strategies for deterministic property control. Knowledge obtained here will facilitate the selection/design of materials with tunable electronic states. It will benefit society by advancing the repertoire of structure-based design strategies to control electronic structure, which could lead to discovery of higher voltage redox couples for better performing energy storage/conversion systems, materials for transparent electronics, and optical technologies relying on laser generated light. Ultimately, interactions with experimental groups will lead to the discovery of functional properties in structurally and chemically more complex (hybrid) in/organic materials than those proposed. The EEP will impact the next-generation workforce by broadening STEM participation, endowing students and teachers